Educational information, not medical advice — ask your doctor or midwife.
Mayweed is a weedy plant in the daisy family. Its botanical name is Anthemis cotula. It is also called stinking chamomile or dog fennel.
It looks a lot like true chamomile. The smell tells them apart. Mayweed smells sharp and foul, and the fresh plant can blister bare skin.
American folk and Eclectic healers once used the dried flowering tops as a tea or a wash. Today the plant is better known as a cause of rashes in farm workers than as a remedy.
The honest verdict: there are no human trials showing that mayweed treats any illness, and it carries a real skin and gut hazard. Long use in folk medicine is not proof that a plant works, and it is not proof that it is safe. That point applies to everything on this page.
No one has shown that mayweed treats a disease in people. What follows is proposed, not proven.
The plant holds anthecotulide, a sesquiterpene lactone (a type of plant chemical). In patch tests and lab work, this compound binds to skin proteins and sets off an allergic reaction. That is the best-documented action of the plant, and it is a harm rather than a benefit.
The volatile oil (the part that gives the strong smell) irritates tissue it touches. Case reports and animal work describe burning of the mouth, gut upset and vomiting after it is swallowed. Whether a small amount does anything useful is simply not known.
Eclectic writers called mayweed a diaphoretic (something that makes you sweat) and an emmenagogue (something that brings on a period). Neither claim has been tested in a modern human trial.
Mayweed is not a mainstream commercial herb. You will not usually find it in a pharmacy or a supermarket.
Where it does appear, it is sold or used as:
Dried flowering tops from wildcraft or foraging suppliers.
Home-made teas or washes, in the old folk pattern.
Alcohol tinctures, mostly in historical Eclectic practice.
An accidental exposure, which is the most common form of all. Farm workers, gardeners and hay handlers meet the fresh plant on their hands and arms.
This page gives no method for making any of these preparations.
Mayweed came to North America from Europe and spread as a field weed. Nineteenth-century American folk healers and Eclectic physicians picked it up as a cheap, common plant.
It was written up as a sweat-promoter for fevers and colds. It was also used for painful or missing periods, and as a bitter tonic for the stomach.
The old texts did not treat it as harmless. Eclectic sources warned that it irritated the stomach, caused vomiting, and blistered the skin of people who gathered it.
Its use faded as safer, better-smelling chamomile became easy to buy.
Some reactions to Mayweed need urgent care. Call your local emergency number or go to an emergency department straight away — do not wait to see whether it passes.
Call emergency services now if you have swelling of the lips, tongue or throat. Do the same for trouble breathing, a tight chest, widespread hives, dizziness or fainting. These can be signs of anaphylaxis, a life-threatening allergic reaction.
Go to urgent care the same day for blisters that are spreading, open weeping skin, or a rash with fever.
Stop and see your doctor for repeated vomiting, blood in vomit or stool, or severe belly pain.
If you cleared this weed and a rash started hours later, tell your doctor exactly which plant you touched.
Mayweed is not approved as a medicine in the United States, the United Kingdom or the European Union. It is treated there as a farm weed, not a crop or a food ingredient. In the US it could in theory be sold as a herbal supplement, but it is rarely offered and has no official safe-use standard.
Do not swap one plant for another on your own. Take these to your doctor, pharmacist or a registered medical herbalist, and name any medicines you already take.
For cramps or period pain, ask your doctor about standard painkillers and about causes worth checking.
For mild digestive upset, ask whether German chamomile or peppermint suits you. These are far better studied and far less irritating than mayweed.
For a cold or fever, ask your pharmacist about simple fluids, rest and over-the-counter options.
For an itchy rash you already have, ask a doctor rather than treating it with another plant.
Graded pages for the options named above:
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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