Ammi majus
Apiaceae
Bishop’s Weed; Bishop’s Flower; False Bishop’s Weed; Bullwort; Greater Ammi; Lady’s Lace; Laceflower; Queen Anne’s Lace; False Queen Anne’s Lace; Ammi majus
Furanocoumarins and psoralens, including 5-methoxypsoralen and 8-methoxypsoralen, also known as bergapten and xanthotoxin; nitrates may also be present. Seeds are generally considered especially toxic.
Photosensitization, sunburn-like skin injury, subacute ulcerative and exudative dermatitis, redness, blistering, swelling, crusting, sloughing, and necrosis of light-exposed or lightly pigmented skin, especially the ears, muzzle, eyelids, vulva, udder, teats, and other sparsely haired areas. Eye signs may include photophobia, cloudy cornea, conjunctivokeratitis, corneal injury, scarring, impaired vision, or blindness. Severe cases may involve secondary infection, fly strike, debilitation, dehydration, and lasting scars or permanent eye damage.
Ammi majus, also known as Bishop’s Flower, Bishop’s Weed, False Bishop’s Weed, Bullwort, Greater Ammi, Lady’s Lace, Queen Anne’s Lace, False Queen Anne’s Lace, and Laceflower, is a commonly grown ornamental annual in the family Apiaceae. Originally introduced from Asia, the plant has become widely established throughout the coastal regions of the southern United States. It produces white, lace-like flower clusters at the end of a 1 to 2 foot stem, giving it the delicate appearance that has made it popular in ornamental plantings, cut-flower use, and naturalized landscapes.
The plant is toxic and poses a risk to both companion animals and agricultural animals. The primary toxins are furanocoumarins, including 5-methoxypsoralen and 8-methoxypsoralen, also known as bergapten and xanthotoxin, respectively. Nitrates may also be present. All parts of the plant should be treated as potentially toxic, but the seeds are of particular concern. Current veterinary references continue to associate Ammi majus with photosensitization, and Merck notes that plants in the Apiaceae family can contain photoactive furocoumarins, or psoralens, capable of producing photosensitization in animals.
Photosensitization has been reported or recognized in companion animals, cattle, sheep, poultry, and humans as a result of ingestion or direct skin contact with the plant followed by exposure to sunlight. This is the critical point with Bishop’s Weed: the plant does not merely irritate the digestive tract like many mildly toxic ornamentals. Instead, it can make the animal’s tissues abnormally reactive to sunlight, producing skin and eye injuries that may be far more severe than the original ingestion would suggest.
Photosensitization is a clinical condition in which areas exposed to light and lacking significant protective hair, wool, or pigmentation become hyperreactive to sunlight due to the presence of photodynamic agents. When animals ingest the plant, the body may be unable to fully metabolize or eliminate the photoreactive compounds before they are deposited or circulated through body tissues. When those tissues are then exposed to ultraviolet radiation from sunlight, the photoreactive compounds become energized.
This reaction yields free radicals that literally “burn” the affected tissue. The exposed tissue may become red, swollen, painful, wrinkled, blistered, split apart, ulcerated, or exudative. In severe cases, the surface may slough away, leaving open wounds. Recovery may take days to weeks, and obvious scarring may remain permanently. Secondary bacterial infection, necrosis, fly strike, dehydration, and the severe systemic stress of extensive skin injury may further debilitate the animal and increase the risk of death in severe livestock or field cases.
The areas most commonly affected are those exposed to sunlight and lacking heavy protective hair or pigmentation, including the ears, eyelids, muzzle, nose, lips, vulva, udder, teats, and other lightly pigmented or sparsely haired regions. Grazing animals may be especially vulnerable because they may ingest larger amounts of the plant and then remain exposed to direct sunlight for prolonged periods.
Even more damaging than the effect on the skin is the potential effect on the eyes. Animals may develop photophobia, cloudy corneas, conjunctivokeratitis, corneal injury, and permanent scarring of the eyes. Severe ocular involvement may leave the animal partially or completely blind. Any animal showing eye pain, squinting, cloudiness, light sensitivity, or apparent loss of vision after exposure to Bishop’s Weed should be treated as a veterinary priority.
Because the toxicity depends heavily on both plant exposure and subsequent sunlight exposure, the first and most important management step is removal from sunlight. Animals suspected of ingesting or contacting Bishop’s Weed should be kept shaded or indoors while veterinary guidance is obtained. For grazing animals, removal from contaminated pasture and housing in a cool, dark place during daylight hours may significantly reduce further injury while the photosensitivity continues.
Immediate Response to Bishop’s Weed Exposure
- Remove the Source: Prevent further ingestion by removing the animal from the plant, pasture, bouquet, seed heads, cut material, or any area containing Bishop’s Weed.
- Remove Plant Material from the Mouth: If the animal is witnessed eating the plant, or if identifiable plant matter is found in the mouth, remove any visible plant material and flush the mouth thoroughly with water.
- Keep the Animal Out of Sunlight: Because Bishop’s Weed can cause photosensitization, immediately keep the animal indoors, shaded, or otherwise protected from direct sunlight while veterinary guidance is obtained.
- Wash Exposed Skin: If the plant contacted the skin, muzzle, lips, nose, eyelids, vulva, udder, or other sensitive areas, gently wash the exposed area with mild soap and water to remove plant sap or residue.
- Protect the Eyes: Watch closely for squinting, cloudy cornea, eye redness, tearing, photophobia, or apparent vision problems. Eye involvement should be treated as urgent because permanent damage or blindness may occur.
- Contact Veterinary Help Promptly: Consult a veterinarian, emergency veterinary clinic, ASPCA Animal Poison Control, or Pet Poison Helpline if ingestion is suspected, if skin or eye signs are present, if a large amount was eaten, or if the exposed animal is a cat, dog, horse, sheep, cow, goat, bird, or other grazing or small animal.
Inducing Vomiting and Decontamination
- No Specific Antidote: There is no specific antidote for Ammi majus ingestion, so treatment is palliative, supportive, and aimed at limiting absorption, preventing sunlight injury, and managing skin or eye lesions.
- Inducing Vomiting in Dogs Only: If ingestion was very recent and the dog is alert, breathing normally, able to swallow, and not showing weakness, collapse, tremors, severe depression, repeated vomiting, neurologic signs, or breathing difficulty, a veterinarian or animal poison-control professional may recommend inducing vomiting with fresh 3% hydrogen peroxide.
- Cat Warning: Hydrogen peroxide should not be used to induce vomiting in cats unless a veterinarian specifically directs it. Cats are more prone to irritation and complications from hydrogen peroxide, and home vomiting attempts may create more risk than benefit.
- Do Not Induce Vomiting in an Unstable Animal: Vomiting should not be attempted in any animal that is weak, collapsed, sedated, having trouble breathing, unable to swallow normally, showing neurologic signs, already vomiting repeatedly, or otherwise unstable.
- Activated Charcoal and Gastric Lavage: Gastric lavage and administration of activated medical charcoal may be useful in reducing absorption when ingestion is significant or recent, but these are veterinary procedures and should be performed under professional direction.
- Cathartics: A cathartic to stimulate elimination may be considered by a veterinarian in appropriate cases, especially where plant material or seeds may still be present in the gastrointestinal tract.
Sunlight Restriction and Field Management
- Strict Shade: While photosensitivity continues, the animal should be kept away from sunlight and fully shaded. Even brief sun exposure may worsen skin injury.
- Livestock Housing: Grazing animals should be removed from contaminated pasture and housed in a cool, dark place during the day. If grazing is necessary, it should occur only during darkness and only in areas free of Bishop’s Weed.
- Pasture Control: Inspect pastures, fence lines, ditches, roadsides, hay, and feed sources for Bishop’s Weed, especially seed heads, because seeds are particularly concerning.
- Light-Colored Animals: Animals with white, lightly pigmented, sparsely haired, or thinly covered skin should be watched especially closely because they are more vulnerable to photosensitization injury.
Skin, Eye, and Wound Care
- Early Inflammation: Corticosteroids given parenterally in the early stages may be helpful, but they should be used only under veterinary direction.
- Skin Lesions: Redness, blistering, ulceration, exudation, sloughing, or necrosis should be managed with appropriate wound care, pain control, hygiene, and veterinary monitoring.
- Secondary Infection: Secondary skin infections and suppurations should be treated with basic wound management techniques and veterinary-directed antimicrobial care when needed.
- Fly Strike Prevention: In livestock and outdoor animals, fly strike must be prevented because open, exudative, or necrotic skin lesions can quickly attract flies and worsen tissue damage.
- Eye Injury: Animals with cloudy corneas, conjunctivokeratitis, photophobia, squinting, tearing, or apparent blindness should be examined by a veterinarian because ocular scarring may be permanent.
Prognosis and Recovery
- General Outlook: The prognosis for animals that receive appropriate treatment and strict sunlight restriction is generally good.
- Recovery Time: Most animals recover in days to weeks, depending on the amount ingested, sunlight exposure, severity of skin injury, and whether the eyes are involved.
- Long-Term Effects: Visible scarring, skin damage, or permanent eye damage may remain for the life of the animal after severe photosensitization.
- Severe Cases: Extensive skin necrosis, secondary infection, fly strike, dehydration, eye involvement, or prolonged debilitation can increase mortality risk, especially in grazing animals.
- Prevention: Prevent further ingestion of the plant, remove animals from contaminated areas, and control Bishop’s Weed in pastures, roadsides, and ornamental plantings accessible to pets or livestock.