Cranesbill

What is Cranesbill?

PubMed returned 15 records for the exact phrase Geranium maculatum on October 10 2026, and not one of them is a controlled human trial. Thirteen are plant ecology, insecticide formulation or citizen-science image processing, and the insecticide papers label a citronellol-rich essential oil "Geranium maculatum L.", a composition that belongs to Pelargonium oil. One is a 1994 Peruvian in vitro screen in which a G. maculatum water extract showed no activity against Vibrio cholerae 01. One is a case series published in the Atlanta Medical and Surgical Journal in October 1889. That is the searchable clinical record for a root still sold in American health food stores as a digestive and oral astringent.

The plant is a woodland perennial in the Geraniaceae, native to eastern North America. The USDA Fire Effects Information System lists it from Ontario and Quebec south to Georgia and west to eastern Oklahoma and the Dakotas, 8 to 24 inches tall, blooming April to June and setting fruit 3 to 5 weeks later. The commercial part is the rhizome: stout, branched, spreading horizontally up to about 6 inches, carrying 10 to 30 sparsely branched roots, at the soil surface under closed canopy and 3 to 4 inches down in open ground. Flower buds form the year before they open. Under a closed canopy only 18.8 percent of plants flower, against 97 percent in full sun.

The genus Geranium holds roughly 422 species. The name comes from the Greek geranos, a crane, after the long beaked fruit capsule. The garden center "geranium" in a window box is not in this genus at all. It is a Pelargonium, split out of Geranium by Charles L'Heritier in 1789 and separable on sight: Pelargonium and Erodium flowers are bilaterally symmetrical, while Geranium flowers have five similar petals in radial symmetry.

Common Names

• Cranesbill, wild cranesbill, spotted cranesbill, American cranesbill

• Wild geranium, spotted geranium (the primary common name in the USDA species review)

• Alum root, alumroot

• Crowfoot, old maid's nightcap, shameface

• Geranii rhizoma, Fluidextractum Geranii (pharmacopeial Latin)

Primary Active Compounds

• Hydrolyzable tannins, reported at 9.72 to 27.85 percent of the dry rhizome by Trimble and Peacock in the American Journal of Pharmacy in June 1891, across 14 collections over two years, by gelatin-alum precipitation

• A gallotannin-type tannin that yields pyrogallol on heating and splits with 2 percent hydrochloric acid into gallic acid, glucose and a red pigment the analysts called geranium red

• Gallic acid, which Trimble and Peacock found absent or in mere traces in the fresh root and its decoction and concluded forms during drying as the tannin breaks down

• Proanthocyanidins, reported as the tannin class that accumulates in the roots of the congener Geranium sylvaticum by Tuominen and colleagues in Phytochemistry 2013

• Starch, pectin, gum, sugar, resin and calcium oxalate

Key Note

Almost nothing in that compound list was measured on Geranium maculatum in the modern era. The USDA phytochemical database carries five entries for the species, all from Duke 1992, and only one of them has a number attached: tannins in the root at 100,000 to 280,000 parts per million, which is 10 to 28 percent. Geraniin, the ellagitannin that gives the genus its best studied marker compound, has been characterized in Geranium sylvaticum and in the Japanese species Geranium thunbergii. I found no published quantification of geraniin in G. maculatum.

This is an astringent drug whose entire active principle is a class of tannins, sold without a tannin number, in a market where the tannin number was measured more carefully in 1891 than it is on any label today.

Primary Functions & Benefits

Cranesbill is a tannin delivery vehicle. Every function attributed to it follows from one behavior, the precipitation of protein by polyphenols, and none below has been measured in a person taking Geranium maculatum.

Surface astringency in the mouth and throat. The effect a user can actually verify. Tannins bind and precipitate salivary proteins, and the resulting loss of oral lubrication is perceived as drying, roughening, puckering and shrinking. Gonzalez-Munoz and colleagues, reviewing the mechanism in the Journal of the Science of Food and Agriculture (2022, volume 102, pages 1771 to 1781), describe three proposed mechanisms rather than one, with tannin binding to salivary proteins only part of the picture. For cranesbill this is a contact effect on a wet surface. Half of Shoemaker's 1889 cases applied it that way, painted on, swabbed on or injected locally; the other half gave it by mouth for consumption, hemoptysis and gastric ulcer, which is where his record is least believable.

Symptomatic antidiarrheal use. The traditional indication across the Eclectic literature, and one that tannin-rich roots elsewhere do hold monographs for: oak bark has a European Medicines Agency monograph for mild diarrhea (EMA/HMPC/3203/2009, adopted November 25 2010). Cranesbill has no equivalent monograph anywhere I could find, and no trial.

Local hemostasis. Shoemaker's most internally consistent 1889 cases were bleeding stopped by direct application: a urethral hemorrhage checked by two 1 drachm injections of fluid extract in 4 drachms of water, and an anal fissure three eighths of an inch long closed by a twice-daily 25 percent solution. Uncontrolled single cases, describing topical use on a visible bleeding surface.

What has not been shown. No effect on gut transit, stool frequency, mucosal healing, blood pressure, lipids, inflammatory markers, oral bacterial counts or wound closure rate has been measured for this species in a controlled human study. The one in vitro screen in the indexed record, Guevara and colleagues in the Revista de Gastroenterologia del Peru in 1994, tested G. maculatum as a decoction or infusion against Vibrio cholerae 01 alongside 13 other plants and reported no effect, while pomegranate peel decoction and tea infusion were bactericidal in the same experiment.

Forms & Standardization

This is the section where cranesbill earns or loses a buyer's money, because the active fraction is a variable percentage of plant mass and nobody on the shelf declares it.

Dried cut or powdered rhizome. The historical pharmacopeial article. Cylindrical, dark brown, odorless, strongly astringent. Trimble and Peacock reported the single most useful dataset ever generated on this plant in the American Journal of Pharmacy (June 1891, volume 63, pages 265 to 267): 14 collections of rhizome dug between May 1 1889 and May 13 1891, almost all from Fairmount Park in Philadelphia, each assayed within 24 hours by precipitating a decoction with gelatin and alum and counting 54 percent of the dried precipitate as tannin. Calculated on the absolutely dry drug: 11.72 percent in January, 27.85 percent just before bloom, 23.44 percent while blooming, 12.38 percent after bloom, 9.72 percent in October. That is a 2.9-fold swing driven by harvest timing, with year-to-year variation layered on top: the before-bloom figure was 27.85 percent in one year and 16.34 percent in the other.

The wider spread between analysts. H. K. Bowman reported 13.41 and 17.25 percent in 1869. Chas. F. Kramer about 17 percent in 1882. Henry J. Mayers in 1889 found 4.25 percent in a commercial powder that had sat in stock, with 8.92 percent of the extract already degraded to phlobaphene, and 11.53 percent in root he powdered himself. Henry R. Procter reported as high as 25.7 percent in 1896. The published range for this root therefore runs from 4.25 to 27.85 percent, a 6.5-fold spread. Duke's 1992 compilation, carried in the USDA phytochemical database, gives 10 to 28 percent. No label states a harvest month, a collection year or a tannin figure, so a buyer cannot locate their own bottle inside that range.

Which tannins, and why the plant part decides it. Here the genus data are more informative than the species data. Tuominen and colleagues characterized 59 polyphenols across eight organs of the congener Geranium sylvaticum (Phytochemistry 2013, volume 95, pages 394 to 407) and found five distinct tannin types: ellagitannins, proanthocyanidins, gallotannins, galloylglucoses and galloyl quinic acids. Geraniin and the other ellagitannins dominated every green photosynthetic organ. The roots and the seeds accumulated proanthocyanidins instead. In the companion paper (pages 408 to 420) the leaves and pistils carried over 30 percent of their dry weight as ellagitannins, while the main roots and hairy roots held high proanthocyanidins in addition to ellagitannins. If that organ pattern holds in G. maculatum, a rhizome product and a leaf product are not the same drug, and the leaf is the ellagitannin-rich part while the commercial part is not.

Geraniin, and the marker the species does not have. Geraniin is the standard marker for medicinal Geranium elsewhere. Japanese Pharmacopoeia 19 carries monographs for Geranium Herb and Powdered Geranium Herb, both from the aerial part of Geranium thunbergii, classified as an antidiarrheal and intestinal regulator and sold in Japan as a third-class risk OTC crude drug, with geraniin named as the major component. So a cranesbill with a live pharmacopeial monograph, a named marker compound and a stated plant part does exist. It is a different species, a different continent and a different plant part from what is in an American cranesbill bottle. I found no published quantification of geraniin in G. maculatum itself.

Fluid extract, 1:1. Professional Formulas sells a cranesbill root extract at 1:1 in 30 percent grain alcohol with a 1 teaspoon serving, which the listing states as 4.9 mL. At 1 g of herb per mL that serving carries about 4.9 g of root equivalent.

Tincture, 1:5. Herb Pharm's wild geranium is made from the rhizome at 1:5 dry herb to menstruum in certified organic cane alcohol at 52 to 62 percent, with a 0.7 mL serving, about 42 servings per 1 ounce bottle, and an extraction rate the company states as 140 mg of herb per 0.7 mL. The herb is described as responsibly wildcrafted. Suggested use is one full squeeze of the dropper bulb in 2 ounces of water or juice, 2 to 4 times a day, "best taken between meals."

The 35-fold gap. Those two label figures are arithmetically comparable and they do not agree. One serving of the 1:1 delivers roughly 4.9 g of root equivalent. One serving of the 1:5 delivers 0.14 g. That is about 35 times more plant per serving from one bottle than the other, and both are correctly labeled cranesbill root extract. A daily comparison is not possible, because the 1:1 label gives no frequency, only "as directed by your healthcare professional." Neither product states a tannin percentage, so the buyer cannot tell which bottle carries more of the only thing in it that does anything.

Standardized extract. None. No cranesbill product I located declares a marker compound or percentage.

What the pharmacopeias used to require. The United States Dispensatory records that geranium was deleted from the United States Pharmacopoeia and was then official in National Formulary IV, where the single official preparation was Fluidextractum Geranii and total ash was required not to exceed 8 percent. That ash ceiling is the only quantitative quality specification this drug has ever carried in an American compendium, it is a limit on mineral matter rather than a measure of potency, and it lapsed when the article left the National Formulary.

Food Sources

Cranesbill rhizome is not a food. There is no dietary intake of it to be sufficient or insufficient, and no culinary tradition that would give a reference serving. What is worth putting numbers on is the surrounding dietary tannin load, because it sets the scale a cranesbill dose has to be judged against.

Everyday galloyl tannin exposure dwarfs a tincture dose. Hurrell, Reddy and Cook measured 274 to 396 mg of polyphenols, as catechin equivalents, in a single 275 mL serving of Assam black tea (British Journal of Nutrition 1999, volume 81, pages 289 to 295). A 0.7 mL serving of a 1:5 cranesbill tincture carries 140 mg of whole root, of which tannin is somewhere between 4 and 28 percent, so the tannin delivered is roughly 6 to 39 mg. Those figures come from different assays (Folin-Ciocalteu against 1891 gelatin precipitation) and are not strictly commensurable, but they differ by an order of magnitude: the cup of tea is the larger polyphenol dose.

Other tannin-dense items in an ordinary diet. In the same eight studies, peppermint tea carried 177 to 209 mg of polyphenols per serving, pennyroyal 121 mg, cocoa 116 mg, lime flower 58 mg and camomile 52 mg.

The one regulated tannin number in US food law. Tannic acid is generally recognized as safe under 21 CFR 184.1097, sourced there from Quercus infectoria nutgalls, Tara pods (Caesalpinia spinosa) and sumac nutgalls, with maximum levels in food as served running from 0.001 percent in meat products to 0.04 percent in frozen dairy desserts and soft candy. Cranesbill is not a listed source and a decoction of its root is not a food category under that section.

The honest comparison. A strong cup of black tea, a tannin-heavy red wine or a decoction of monographed oak bark will each put more galloyl tannin on an oral surface than a dropperful of tincture will, and two of them are cheaper. The argument for cranesbill specifically has to rest on something other than tannin quantity, and no published work establishes what that something is.

Who Should Take Cranesbill

Nobody needs cranesbill: no physiological requirement for it exists and no condition has been shown in a trial to respond to it. It is a defensible purchase for a narrow group, an adult wanting a short-term astringent for a mild self-limiting surface complaint they can see or feel, who accepts that the evidence is an 1889 case series.

Plausible candidates. An adult with mild short-lived loose stools and no fever, no blood and no dehydration. An adult wanting an astringent mouth rinse for minor gum or throat soreness, where the effect is immediate and self-evident.

Who should look elsewhere first. Anyone whose actual goal is diarrhea in a child, hemorrhoids, heavy menstrual bleeding or a wound. Each of those has either a monographed herbal option with a stated dose and a duration cap, or a conventional treatment with trial support, and cranesbill has neither.

Who Should AVOID or Use Caution

Contraindications

• Children and adolescents under 18. The closest governed analog, the EMA oak bark monograph, states that use under 18 is not recommended, and that is for a bark with a monograph and a dose. Cranesbill has no pediatric data of any kind.

• Pregnancy and breastfeeding. No reproductive toxicity data on Geranium maculatum, no human exposure data, no monograph anywhere setting a position. Absence of a signal here is absence of a study.

• Diarrhea with blood, mucus, fever, severe abdominal pain or signs of dehydration, and diarrhea lasting more than two or three days. An astringent that firms stool can flatten the one symptom a clinician would use to judge severity.

• Iron deficiency anemia under treatment. The best quantified hazard attached to any tannin.

Use Caution

• Anyone taking an oral iron supplement, and anyone who is pregnant, menstruating heavily, donating blood regularly, or relying on plant sources for iron.

• Anyone with inflammatory bowel disease, an active peptic ulcer, or a recent gut surgery. Concentrated tannins precipitate protein on contact, including on an already inflamed or raw mucosa, and no study has looked at what that does.

• Anyone with hemorrhoidal bleeding who has not had the cause assessed. The oak bark monograph permits hemorrhoid use only after serious conditions have been excluded by a doctor, and that condition is the useful part of the monograph.

• Anyone taking a narrow therapeutic index oral medication within two hours of a dose, and anyone with a known Geraniaceae allergy. I found no published case of cranesbill allergy, so the second is caution by family membership rather than by report.

Critical Safety Point

The real danger with cranesbill is not the plant, it is the delay. I could locate no documented case of serious poisoning from Geranium maculatum, and a PubMed search pairing Geranium with hepatotoxicity returns five records: four rat studies reporting a protective effect from a different species or from Pelargonium oil, and one in vitro screen of Geranium molle on cultured liver cells. None reports an injury. The harm pathway runs through substituting an untested astringent for a diagnosis: rectal bleeding treated as a hemorrhoid, infectious diarrhea treated as plumbing, a mouth ulcer that will not heal painted with tannin for weeks. Shoemaker's Case 3 is the template: under three weeks of improvement, then death inside five months from a disease the geranium was never going to touch.

Recommended Dosages

No dose for cranesbill has ever been set by a trial, and the numbers below exist for a different reason in each case. Read each one for what it is.

Historical compendial doses, for reference only. These are nineteenth and early twentieth century prescribing figures for a physician-administered drug, recorded in works that are now historical documents, not current recommendations. King's American Dispensatory (1898) gives powdered root at 20 to 30 grains, decoction at 1 to 2 fluid ounces, and specific geranium at 5 to 30 drops. The United States Dispensatory gives 15 to 30 grains, which it converts as 1 to 2 g, for the National Formulary IV article. Shoemaker in 1889 used the fluid extract at a teaspoonful to two drachms by mouth and 20 to 25 percent aqueous solutions topically.

Current label directions, as directions rather than evidence. The Herb Pharm 1:5 rhizome tincture directs adults to one dropper squeeze, a 0.7 mL serving carrying 140 mg of herb, in 2 ounces of water, 2 to 4 times a day, best taken between meals. That works out to about 0.28 to 0.56 g of root equivalent per day. The 1:1 fluid extract product uses a 1 teaspoon serving, about 4.9 g of root equivalent, which is an order of magnitude more per serving.

The nearest number anyone has actually governed. For the same indication in a comparable drug, the EMA oak bark monograph sets 3 g of comminuted bark in 250 mL of water three times daily, a 9 g daily herb dose, or a 140 mg dry extract four times daily. The cranesbill tincture directions land roughly 16 to 32 times lower in herb equivalent, so the two are not aiming at the same thing.

Duration

Short. The only duration limits written down for this class are the oak bark monograph's: no more than 3 days for diarrhea and no more than 1 week for mouth, skin and hemorrhoidal use. Nothing in the cranesbill literature supports open-ended daily use, nothing has looked at what months of concentrated tannin does to iron status, and no product I examined states any limit at all.

Timing & Administration

Away from meals, and away from iron. The Herb Pharm label's "best taken between meals" is the right instruction for the wrong stated reason: the point is to keep a protein-precipitating polyphenol away from the iron and the protein in food. Brune and colleagues showed the inhibition is dose-related down to very small amounts, so the separation matters more than the size of the dose.

Diluted, not neat, and held in contact. Tannins at tincture strength are harshly astringent on mucosa, and both labels direct dilution. Because the effect is a surface effect, swishing a diluted dose is what the 1889 topical cases were doing with 20 and 25 percent solutions painted on.

For loose stools, the fluid comes first. Oral rehydration is the intervention with evidence; an astringent is an optional comfort measure taken after fluid replacement rather than instead of it.

Timeline of Effects

Onset, astringency: seconds. The oral drying and puckering is a direct interaction with salivary proteins, perceptible on the first dose. If a diluted dose does not taste astringent, the product is weak or degraded.

Onset, gut effect: unknown for this species. No trial has timed it. For the nearest measured comparator, Subbotina and colleagues gave tormentil root extract, another tannin-rich astringent rhizome, to hospitalized children with rotavirus diarrhea (Pediatric Infectious Disease Journal 2003, volume 22, pages 706 to 711): 40 children, 20 per arm, randomized and double blind, treated for at most 5 days. Diarrhea lasted 3 days on extract against 5 on placebo (p less than 0.0001), and 8 of 20 children on extract were diarrhea-free at 48 hours against 1 of 20 on placebo. That is tormentil, in children under hospital supervision, and it is not evidence about cranesbill, nor a dosing template for it. It is the shape a fair trial of this kind of root takes.

What counts as a fair trial of cranesbill. Three days, which is the oak bark monograph's ceiling for diarrhea, and one week for a mouth or skin complaint. If a mild self-limiting complaint has not settled inside that window it was not the sort of complaint an astringent addresses, and the next step is a diagnosis.

When to stop. At three days for stools, at one week for anything oral or topical, and immediately if stools turn bloody, a fever appears, or the complaint worsens. There is no loading period to wait out and no mechanism by which weeks of dosing would succeed where three days failed.

Benefits of Taking Cranesbill

The honest benefit list is short, local and unquantified.

A reliable astringent sensation on a wet surface. Real, immediate, verifiable by the user, and equally available from oak bark, tormentil, black tea and witch hazel, three of which have a monograph or a controlled trial behind them.

A traditional antidiarrheal with a long domestic record. John Uri Lloyd, in The History of the Vegetable Drugs of the U.S.P. (1911), described cranesbill as an astringent domestic remedy taken as infusion or decoction for diarrhea, dysentery and sore mouth, and as well established in Eclectic publications. That records how widely it was used, not whether it worked.

A low apparent risk profile at label doses. I found no serious adverse event attributable to the plant and no case report of organ injury from any Geranium species, so the downside of a three day trial at tincture doses appears small. That is a statement about absent reports, which for a herb this little studied is weaker reassurance than it sounds.

What is not on the list. Wound healing rate, hemorrhoid resolution, menstrual blood loss, blood sugar, blood pressure, gum disease scores and infection clearance have all been claimed for this plant in retail copy, and none has been measured in a human taking it.

Potential Negatives & Side Effects

Reduced non-heme iron absorption. The best quantified consequence of taking concentrated tannin by mouth, and the one most likely to matter over weeks. Brune, Rossander and Hallberg fed measured doses of tannic acid with a test meal and tracked iron absorption by extrinsic radio-iron tag (European Journal of Clinical Nutrition 1989, volume 43, pages 547 to 557): 5 mg of tannic acid cut absorption 20 percent, 25 mg cut it 67 percent, and 100 mg cut it 88 percent. The effect tracked galloyl group content.

Oral and gastric irritation. Nausea and stomach discomfort are the predictable complaints at higher doses of any strong tannin preparation, and the 1889 record instructs one patient to continue the fluid extract "regardless of whether vomiting or hemorrhages supervened," which tells you vomiting was expected at the doses then used.

Reduced protein and enzyme availability in the gut. Tanaka, reviewing tannin chemistry in Yakugaku Zasshi in 2024 (volume 144, pages 183 to 195), notes that tannins precipitate proteins and deactivate digestive enzymes, which is why they function as plant defense compounds. For a short course this is unlikely to matter. For habitual high intake with meals it is the mechanism by which tannins reduce the nutritional value of a diet.

The side effect nobody lists. A product with no marker assay and no stated harvest month can be 4 percent tannin or 28 percent tannin. The adverse event a buyer is most likely to experience is paying for the 4 percent bottle.

Deficiency Symptoms

What cranesbill deficiency addresses

Nothing. Geranium maculatum is not a nutrient, has no established role in human physiology, and no deficiency state exists for it. Contrast a genuine trace element: iron has a measurable status marker in serum ferritin, a defined deficiency syndrome, and a published requirement. Cranesbill has none of the three, and the one quantified thing tannins do to iron status works in the wrong direction.

Bottom line

If you stop taking cranesbill, nothing is lost but the astringency.

Toxicity Symptoms

At high intake

No toxic dose has been established for Geranium maculatum, and no human overdose case appears in the record I searched. The nearest acute toxicity figure in the genus comes from a different species in rats: Gayosso-De-Lucio and colleagues reported an LD50 above 5,000 mg/kg for an acetone-water extract of Geranium schiedeanum by the Lorke method (Pharmacognosy Magazine 2014, volume 10, supplement 3, pages S574 to S580). That is an animal number for another species and it is not a guide to any human amount.

Signs to reduce or stop

• Nausea, vomiting or epigastric burning after a dose

• Stools that become hard or stop, after loose stools resolved

• Mouth or throat soreness that worsens with continued rinsing

• Fatigue, breathlessness on exertion or pallor developing over weeks of daily use, which would warrant a ferritin check rather than a dose adjustment

• Any blood in stool, fever, or weight loss at any point, which is a reason to stop and be examined rather than to reduce

General note

The hazard with this plant scales with duration and with concurrent iron needs, not with a single large dose. Nothing in the tannin literature suggests a dramatic acute toxicity, and nothing in it supports taking a strong galloyl tannin with every meal for months either.

How Cranesbill Works

One mechanism, protein precipitation, which is also the taste. Tannins are defined by forming insoluble complexes with protein. That single behavior accounts for the astringent taste, the traditional antidiarrheal and hemostatic uses, the iron interaction, and the plant's own defense against herbivores and soil pathogens.

Structure decides potency, not bulk percentage. This is what makes an 1891 tannin percentage less useful than it looks. Engstrom and colleagues tested 32 purified and structurally characterized hydrolyzable tannins against bovine serum albumin in a turbidimetric 96-well assay (Journal of Agricultural and Food Chemistry 2019, volume 67, pages 6798 to 6808). Precipitating power depended on molecular weight, the number of galloyl groups, the degree of oxidative coupling between those galloyls, positional isomerism, and whether the glucose core was cyclic or acyclic. Oligomers outperformed monomers, and for oligomers size and flexibility mattered more than functional groups. The practical reading: two roots assaying at the same total tannin can differ substantially in how much protein they actually precipitate, and no bulk tannin number distinguishes them.

Which is why the plant part matters. On Tuominen's organ pattern the rhizome is proanthocyanidin-led and the leaf geraniin-led, and those classes differ in both precipitation behavior and iron binding.

At the mucosal surface. The traditional account is that tannins cross-link surface proteins into a thin coagulated layer that reduces secretion and permeability. For the mouth this is partly characterized: astringency is a tactile percept of lost lubrication and increased oral friction after salivary proteins are bound, and Gonzalez-Munoz and colleagues note it involves more than tannin-protein binding alone. For the gut mucosa the coagulation account remains traditional pharmacology. It has not been imaged, quantified or confirmed in a human for this plant or, as far as I could establish, for any cranesbill preparation.

The iron mechanism is specific, and it is about galloyl groups. Brune and colleagues found that gallic acid inhibited iron absorption to the same extent as tannic acid per mole of galloyl groups, that chlorogenic acid inhibited less, and that catechin added to a test meal produced no inhibition at all. They concluded that iron-binding galloyl groups are the major determinant and that condensed tannins do not interfere with iron absorption. That conclusion rests on catechin, a flavan-3-ol monomer, rather than on oligomeric proanthocyanidins, so it should not be stretched into a clean bill of health for a proanthocyanidin-rich root.

Tannins are not stable, and that is a mechanism too. Tanaka's review documents ellagitannins undergoing oxidative degradation as leaves mature, in whiskey aging in oak barrels, and in wood decaying in forests. Geraniin specifically is described by the group that worked on it as not a stable compound and difficult to obtain, which is why they prepared a stable acetone condensate instead. The nineteenth century analysts were watching this directly: Mayers' low 1889 sample contained phlobaphene, the insoluble red product of tannin decomposition, and Trimble and Peacock found no gallic acid in the fresh root or its decoction and concluded it appears during drying as the tannin breaks apart. A cranesbill product is a decaying chemical system from the day the root leaves the ground.

What does not happen. Hydrolyzable tannins of this size are poorly absorbed intact, and no pharmacokinetic study of any cranesbill preparation exists in any species. Every systemic claim for this plant rests on no measurement of it reaching the circulation.

Synergistic Supplements

No combination containing cranesbill has been tested in a human. What follows is reasoning from the mechanism, labeled as such.

Oral rehydration salts. The genuinely useful pairing for loose stools: fluid and electrolyte replacement is the part with evidence, and the astringent is the optional comfort layer.

Other tannin astringents, with caution rather than enthusiasm. Oak bark, tormentil and witch hazel work by the same mechanism, so stacking them multiplies the galloyl load rather than adding a second mode of action. If the goal is more astringency, the monographed option with a dose is the better buy.

Vitamin C, taken with the iron and not with the tannin. Ascorbic acid is the best established counter to polyphenol inhibition of non-heme iron absorption, so someone who needs both should separate them.

What not to combine it with. Iron, zinc and any protein supplement in the same mouthful. A protein shake is protein, and precipitating protein is the mechanism.

Interactions & What NOT to Take

Oral iron salts: ferrous sulfate, ferrous gluconate, ferrous fumarate, iron bisglycinate. The one interaction with human numbers behind it. Separate by at least two hours. On the Brune data a tannin load in the tens of milligrams is enough to cut absorption by two thirds, and the cranesbill serving sizes above sit in that range on the published tannin percentages.

Black tea, green tea, coffee, cocoa and red wine. Not drugs, but additive on the same mechanism. Hurrell measured 79 to 94 percent inhibition from Assam black tea, and even a 5 percent strength tea carrying about 20 mg of polyphenols still inhibited by about two thirds. Adding a tincture to a tea habit compounds an already large effect.

Levothyroxine and alendronate. Both are dosed on an empty stomach precisely because they bind in the gut lumen. Keep a tannin preparation well clear of them.

Digoxin, warfarin and lithium, plus doxycycline and ciprofloxacin. No cranesbill interaction study exists for any of them. Binding in the gut lumen is a documented problem for the two antibiotics with dietary cations and polyphenols, and the first three have narrow margins. Two hours of separation, and tell the prescriber.

Protein-containing supplements and meals. Whey, collagen and casein powders will be partly precipitated by a tannin taken alongside them, and both the protein and the tannin lose.

What there is no evidence for. I found no reported interaction between Geranium maculatum and any named drug. Every item above is mechanism-based extrapolation from tannin chemistry, and I am labeling it that way rather than presenting it as a documented interaction.

Quality, Testing & Adulteration

The word "geranium" has already been used once to launder a synthetic stimulant. This is the most consequential adulteration episode attached to the name, and it did not involve this plant. 1,3-dimethylamylamine, DMAA, was sold in pre-workout supplements on the claim that it occurs naturally in geranium, meaning Pelargonium graveolens. FDA's position is that it is not aware of any reliable science showing DMAA occurs naturally in plants, and its public listing records 18 warning letters beginning in 2012, ten of them dated April 24 2012, USP Labs among the recipients. In 2013 FDA administratively detained USPLabs' OxyElite Pro and Jack3d, and the company destroyed product estimated at over $8 million retail. Hi-Tech Pharmaceuticals contested a seizure; a federal district court ruled the products adulterated in April 2017, the Eleventh Circuit affirmed in 2019, the Supreme Court denied review in 2020, and the products were destroyed on November 12 2020. FDA names raised blood pressure, arrhythmias, heart attack and seizures among the harms.

The analytical record there, read with discipline. Li and colleagues reported 1,3- and 1,4-DMAA in Chinese-sourced geranium plant and oil by LC-ESI/MS/MS, with a quantification limit of 1 to 2 ng/g (Analytical Chemistry Insights 2012, volume 7, pages 47 to 58). Avula and colleagues did not detect it in authentic P. graveolens plant material or in pelargonium oils at a 10 ng/mL detection limit, while detecting it in three supplements (Journal of AOAC International 2015, volume 98, pages 757 to 759). A non-detect at a stated limit is not a zero, and a quantification limit is not a content. Gauthier (2013, same journal, volume 8, pages 29 to 40) attributed the conflict to source material, extraction and analytical approach. The lesson for a cranesbill buyer is about the label word: "geranium" has already proved elastic enough to cover something that was not in a plant at all.

"Alum root" is shared across two families. King's American Dispensatory gives alum-root and American sanicle as the common names of Heuchera americana, which is a Saxifragaceae, not a Geraniaceae. It records that some practitioners used Heuchera root interchangeably with Geranium maculatum, and that Heuchera is the more powerfully astringent of the two. Peacock found 5.55 percent tannin plus 12.2 percent phlobaphene in Heuchera, with October-collected roots highest at 19.66 percent on a dry basis, and Bowman reported about 20 percent in 1869. So a jar labeled "alum root" with no binomial could reasonably be either of two astringent roots from two different plant families, both historically sold for the same purpose, with the non-Geranium one described by the period literature as the stronger.

And "cranesbill" and "geranium" are shared more widely still. Within medicinal and commercial use alone the name attaches to Geranium thunbergii (the Japanese Pharmacopoeia article), G. sylvaticum, G. robertianum, G. wilfordii (in a registered oncology trial), G. molle, G. macrorrhizum and G. schiedeanum, while "geranium" in a garden center, an essential oil bottle and a respiratory supplement means Pelargonium.

What the law actually gives the buyer. FDA amended 21 CFR 101.4(h) by final rule published August 28 2003. A botanical dietary ingredient must be identified by a standardized common name consistent with Herbs of Commerce, 2nd Edition (2000), or, where no standardized common name is listed there, by its Latin binomial in parentheses following the International Code of Botanical Nomenclature (Saint Louis Code) 2000. The label must also state the part of the plant the ingredient came from, in English. Those two items, the part and the name, are the only species-level assurances written into American supplement labeling, and both are checkable on the shelf in ten seconds.

What third-party certification can and cannot do here. USP, NSF and ConsumerLab programs test a product against a specification: stated identity, stated potency, contaminant limits. Cranesbill has no current compendial specification, having left both the USP and the National Formulary. A certification mark can therefore attest that a bottle is free of heavy metals and microbes and contains what the manufacturer said, not that what the manufacturer said is enough tannin to do anything. Pharmacopeial monographs also tolerate some foreign organic matter by design, 2 percent in USP, so even a compliant botanical article is not pure target species.

The published mislabeling rate, and the retraction inside it. Ichim pooled 206 peer-reviewed studies covering 5,957 commercial herbal products sold in 37 countries and found 27 percent adulterated by DNA-based methods (Frontiers in Pharmacology 2019, volume 10, article 1227), with 134 of 465 United States products adulterated (29 percent) and 39 of 55 Canadian products (71 percent). Two cautions belong with that figure. The pooled data set includes Newmaster and colleagues' 2013 study of 44 North American herbal products (BMC Medicine volume 11, article 222), which BMC Medicine retracted on July 4 2024 after the University of Guelph found evidence of data fabrication; four of the authors disagree with the retraction. And Ichim's own stated limitation cuts the other way for a product like this one: DNA-based methods produce false negatives when DNA has been degraded or lost during processing, which is exactly what happens in a hydroalcoholic tincture. Neither the pooled rate nor any DNA method has been applied to cranesbill specifically in anything I located.

On the certificate of analysis. Ask for the Latin binomial with the identity method named, the plant part, the harvest month and year, total tannin with the assay method stated, heavy metals, microbial counts, and the extraction solvent and final ethanol percentage. The harvest month is the unusual request, and the one with 1891 data behind it.

What you can settle for yourself, standing in the aisle. Four things. Whether the label names the part, and whether it says rhizome or root rather than herb or leaf. Whether it gives Geranium maculatum in parentheses, or a bare common name that could belong to another genus or another family. Whether it states an extraction ratio, which lets you compute herb equivalent per serving and compare two bottles honestly. And, once home, whether a diluted dose tastes sharply astringent, because tannins degrade and taste is the only potency feedback this product category offers you.

Special Considerations

Wildcrafted supply, and what that implies. The Herb Pharm material is described as responsibly wildcrafted in the United States, and wild collection is the norm for this root. G. maculatum first blooms in its second or third year, disperses seed an average of 10 feet and at most 30, and can hold seed dormant for more than 400 days. Harvest takes the rhizome, so recovery depends on fragments left behind and on a slow seed route.

Season is the hidden variable in every bottle. On the Trimble and Peacock curve, October-dug root carried roughly a third to three fifths of the tannin of root dug just before bloom, depending on the year, and conventional root harvesting is an autumn job. No label states the month.

Not the plant in the respiratory supplements. A customer who has read about Pelargonium sidoides for colds, which does hold an EU herbal monograph (EMA/HMPC/648100/2022, Revision 2, first published October 16 2023, traditional use, common cold symptoms), is not buying a related product when they buy American cranesbill.

Research Status & Evidence Quality

Tier 1, randomized controlled human trials: none. Zero for Geranium maculatum in any indication, on PubMed, PubMed Central and ClinicalTrials.gov as searched on October 10 2026.

Tier 2, controlled or observational human studies: none located. No cohort, no case-control, no open-label series after 1889.

Tier 3, uncontrolled human case reports: one document. Shoemaker's ten cases, 1889, no controls, no blinding, mixed outcomes including one death.

Tier 4, in vitro work on this species: one negative screen. Guevara 1994, G. maculatum water extract inactive against Vibrio cholerae 01 in a panel of 14 plants.

Tier 5, chemistry: historical, and strong for its era. Trimble and Peacock's 1891 seasonal series remains the best quantitative work ever done on the drug, and modern compound-level characterization of this species appears not to exist. What circulates as cranesbill chemistry is extrapolated from G. sylvaticum, G. thunbergii, G. molle, G. macrorrhizum and G. schiedeanum.

Tier 6, genus and class evidence: moderate and genuinely useful. Tuominen 2013 on organ-specific tannin distribution, Engstrom 2019 on protein precipitation structure-activity, Brune 1989 and Hurrell 1999 on galloyl tannins and iron, plus the monographed comparators oak bark and G. thunbergii. This tier is where everything defensible here comes from, and none of it was measured on this plant.

Research Limitations

The limits of my own search belong here. I searched PubMed and PubMed Central by species name and by common name, and ClinicalTrials.gov by species name, common names and family, on October 10 2026. I did not search Embase, CINAHL, CNKI, J-STAGE, the Cochrane Library, the WHO International Clinical Trials Registry Platform, the EU Clinical Trials Register, or non-English literature beyond what those two databases index. A trial of American cranesbill could sit in one of them, and the pre-1950 Eclectic and homeopathic literature is largely unindexed by any of them. The accurate statement is therefore narrow: in the databases named, on that date, there is no controlled human trial of this species. I also could not read the Herbs of Commerce 2nd Edition entry to confirm which of cranesbill, wild geranium and alum root is the standardized common name. The Trimble and Peacock figures were checked against the 1891 paper itself, and Mayers' against his 1889 paper.

Summary & Key Takeaways

Bottom Line

Cranesbill is a tannin astringent whose clinical file closed in 1889 and never reopened. Its one verifiable effect, protein precipitation on a wet surface, is real, immediate, and available more cheaply from oak bark, which has a monograph, a dose and a three day limit. It is sold without a tannin figure in a market where that figure was measured across 14 collections in 1891 and ranged from 9.72 to 27.85 percent by harvest month, and where two products carrying the same front label differ 35-fold in plant per serving.

Key Safety Points

• Galloyl tannins block non-heme iron absorption steeply and at small doses: 25 mg of tannic acid cut absorption 67 percent in Brune's test meals. Separate from iron by two hours, and reconsider daily use entirely if you are iron deficient, pregnant or menstruating heavily.

• Not for anyone under 18. The monographed analog excludes that group and cranesbill has no pediatric data at all.

• Not for pregnancy or breastfeeding, on no data rather than on reassuring data.

• Three days for stools, one week for mouth or skin. Blood, fever, severe pain or dehydration means stop and be examined.

• The real risk is a missed diagnosis behind a suppressed symptom, not the plant.

Special Note

Check the part and the name. Federal law requires the plant part in English and either a standardized common name or the binomial in parentheses, and "alum root" alone can mean Heuchera americana in the Saxifragaceae, which the period literature called the stronger astringent of the two. "Geranium" in a supplement aisle has meant a Pelargonium, and in the pre-workout aisle it once fronted for DMAA, which FDA says it has seen no reliable science placing in any plant. If the bottle does not say Geranium maculatum and does not say rhizome, you do not know what you have bought.

Researched and drafted with AI assistance. Every claim verified against primary sources and human-reviewed before publication. Last reviewed: October 15, 2026. Corrections: reply to any issue.

This issue is educational and is not medical advice. It does not diagnose or treat anything. If you take prescription medication, are pregnant or breastfeeding, or have a diagnosed condition, talk with a clinician before adding or stopping cranesbill or any other supplement.