Allergic dermatitis–simply, inflammation of the skin caused by an irritating stimulus–is a common yet often treatable and manageable problem in horses. Ann Rashmir-Raven, DVM, MS, Dipl. ACVS, associate professor of Large Animal Clinical Sciences at Michigan State University's College of Veterinary Medicine, gave an overview of the disorder at a recent veterinary convention.

At the 2012 Western Veterinary Conference, held Feb. 19-23 in Las Vegas, Nev., Rashmir-Raven explained that a wide variety of irritants can cause allergic dermatitis. She reviewed a few of the common causes and management options during her presentation.

Urticaria–Even if you've never heard the word before, chances are you've seen the ailment it describes: hives. Rashmir-Raven said that horses develop urticaria more than any other species, and veterinarians believe the condition is most commonly caused by insect bite hypersensitivity (other less common causes include contact dermatitis and drug reactions–more on those in a moment).

"In addition to hives, insect bite hypersensitivity can also manifest as intensely pruritic (itchy) dermatitis and is usually seasonally recurrent, although severely affected horses in Southern climates do not enjoy seasonal relief," she explained, adding that the condition often worsens with age