Can Horses React to Poison Ivy and Poison Oak?

Q: There is quite a bit of poison oak and poison ivy on the acreage where I keep my horses. I have recently added a 2-year-old Thoroughbred mix, and she immediately broke out on her legs and muzzle with small rash-like, raised bumps that remind me of my allergic reactions to poison oak. I am trying to isolate her from it, but it is difficult, as it seems to be everywhere that I can turn her out. Any recommendations, including suggested treatment?        Robin

A: Poison ivy appears to be a problem to some humans only. Horses, cattle, sheep, and goats are rarely (if ever) affected, and I am not familiar with any reports in the literature of poison ivy affecting horses. A large number of birds and wildlife feed on poison ivy, and horses and livestock graze on it without problem. The toxic oil (urushiol) from poison ivy, poison oak, and poison sumac can, however, contaminate animals' hair and be a hazard to people handling them.

It is doubtful the allergic skin reaction in your horse is due to poison ivy. The use of an appropriate herbicide recommended by your local weed control extension service specialist might be helpful in reducing the poison ivy in your pasture. Your horse might also enjoy the company of a goat or two that would help graze the poison ivy and poison oak. You should contact your veterinarian to determine what caused your filly to break out, since it is doubtful it was the poison ivy.

About the Author

Anthony Knight, BVSc, MS, Dipl. ACVIM

Anthony P. Knight, BVSc, MS, Dipl. ACVIM, is a professor of large animal medicine in the College of Veterinary Medicine and Biomedical Sciences at Colorado State University. He received his veterinary degree from the University of Nairobi, Kenya, in 1968. After completing a master’s degree at Colorado State University, he joined the faculty in 1974. His current professional interests include livestock heath, foreign animal diseases, emergency management, and plant toxicology. He has written two books on poisonous plants of animals in North America, and maintains a poisonous plants website for use by anyone wanting poisonous plant information.

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