Home / Safety / Toxic Plants / Mayweed (Stinking Chamomile)
Toxic to dogs. The ASPCA lists mayweed (stinking chamomile) as toxic to dogs. Low tier for one encounter, worth respect for a habit. A rash plus stomach signs after grazing weedy ground earns a call; a dog grazing it daily in a yard or paddock needs the plant removed and a vet conversation about the long term note.
Mayweed, also stinking chamomile and poison daisy, is the white daisy weed of farmyards, gateways and disturbed ground, flowering from spring to fall and smelling rank when crushed. It impersonates harmless chamomile and daisies, which is exactly how it gets grazed without concern. The ASPCA lists it as toxic to dogs, and its folk name, poison daisy, is the honest one of its three names.
Look for a bushy annual weed with finely divided, feathery leaves and many small white daisy flowers with yellow centers on branching stems. Crush a leaf: mayweed smells sharp and unpleasant, unlike the apple scent of true chamomile. It colonizes bare, compacted ground: kennel runs, gateways and worn paddock corners.
The ASPCA names the toxic principle of mayweed (stinking chamomile) as Volatile oil containing bisabolol, chamazulene, anthemic acid and tannic acid. Mayweed is the chamomile family's bad neighbor: a daisy weed whose volatile oils irritate skin on contact and the gut when eaten, with allergic reactions in the mix. The ASPCA sign list runs from contact dermatitis through vomiting, diarrhea and loss of appetite, and adds a long view warning: long term use can lead to bleeding tendencies. A single graze is an irritant event; a dog living in a mayweed filled paddock and eating it daily is a different, slower problem.
The clinical signs the ASPCA lists for mayweed (stinking chamomile) are: contact dermatitis, vomiting, diarrhea, loss of appetite and allergic reactions; the ASPCA notes long term use can lead to bleeding tendencies. Contact and grazing combine in the usual case. A dog lying and rolling on mayweed covered worn ground picks up the dermatitis on belly and paws, then grooms and swallows the oils, adding vomiting and diarrhea. Skin signs and stomach signs together, in a dog whose run has gone weedy with white daisies, should put this plant on the list you give the veterinarian.
Most dangerous part: The flowering tops and foliage in repeated contact or repeated grazing. The plant's strong, rank smell is its own warning label that dogs, unfortunately, do not read.
The chamomile confusion deserves a sentence of its own, because true chamomile has its own ASPCA entry as a toxic plant too, under garden chamomile. The daisy patch by the gate is not a safe corner whichever of the two it is: identify it by smell, photograph it, and clear it from dog ground.
Call your veterinarian, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661 right away, even if your dog looks fine. Some poisons take hours or days to show their worst effects. Do not make your dog vomit unless a veterinarian tells you to, and keep the packaging, a photo, or a sample of what was eaten to show the clinic.
Clear mayweed from kennel runs, gateways and the worn corners dogs rest on, pulling it with gloves before it seeds, and reseed or mulch the bare ground it favors. A grazing dog in a weedy paddock needs the weeds managed, not just this one, because the daisy family lookalikes travel together.
For worn dog ground, the alternative is groundcover management rather than a swap plant: grass cover, mulch or gravel in resting corners removes the bare soil mayweed needs. Any flowering replacement for a border should be verified as non-toxic on the ASPCA list. Whatever you plant next, check it on the toxic plants index approach: confirm the plant on the ASPCA toxic and non-toxic list under its scientific name, Anthemis cotula is the name to avoid here, before it goes in the ground or on the shelf.
Yes. The ASPCA lists mayweed (stinking chamomile) (Anthemis cotula) as toxic to dogs. Its toxic principle is Volatile oil containing bisabolol, chamazulene, anthemic acid and tannic acid, and the signs it lists include contact dermatitis, vomiting, diarrhea, loss of appetite and allergic reactions; the ASPCA notes long term use can lead to bleeding tendencies.
Call your veterinarian, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661 straight away. Note what part of the plant was eaten and roughly how much, keep any remaining plant material to show the clinic, and do not make your dog vomit unless a veterinarian tells you to.
The flowering tops and foliage in repeated contact or repeated grazing. The plant's strong, rank smell is its own warning label that dogs, unfortunately, do not read.
Smell is the field test: crushed mayweed smells rank and sharp, true chamomile smells faintly of apples. For a dog the practical answer is simpler, because both carry ASPCA toxic listings: clear the daisy weed from dog ground and do not let the dog graze either.
The ASPCA notes that long term use of mayweed can lead to bleeding tendencies. A single graze is not that pattern; a daily habit is. If your dog has grazed it for weeks, tell your veterinarian, who can judge whether blood work is warranted.
This page is general information drawn from the published guidance of the organizations listed under Sources below. It is not veterinary advice, and it does not replace your own veterinarian, who knows your dog. If your dog has eaten something toxic, contact your veterinarian, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661 straight away. A consultation fee may apply on the helplines.
Last updated: November 2026. Every verdict on this page was checked against the sources listed above. How we work: our methodology.
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