What poison ivy has against us

A severe allergic skin reaction to poison ivy is almost exclusively a human problem, and for some animals the leafy plant is even a dietary delicacy.

Q: Are any animals besides humans affected by poison ivy?

A: A severe allergic reaction when the skin is exposed to poison ivy is almost exclusively a human problem.

Some sensitive higher primates react to poison ivy to some extent, as do guinea pigs, which often resemble humans in their allergic reactions. There are also anecdotal reports of dogs experiencing discomfort after hairless skin areas touch bruised poison ivy.

For part of the mammalian world, however, poison ivy, Toxicodendron radicans, is a food, even a choice delicacy. The list of mammals that enjoy it includes white-tailed deer, raccoons, muskrats and Eastern cottontail rabbits.

It is also fancied by some birds, including the wild turkey, American robin, Northern bobwhite, Eastern bluebird, mockingbird, white-throated sparrow, Carolina wren and European starling.

The substance that causes the problem for people is an oily compound called urushiol, found in many cells of the poison ivy vine. Exposure to this allergen brings white blood cells to the site, and their overvigorous response to the foreign substance leads to an attack on skin cells as well, producing a rash, with blisters where the concentration is highest.

It is believed that urushiol is the poison ivy plant’s physical armor against the many kinds of insects that feed on it, quickly sealing the wounds with a tarry plug.