Contact Dermatitis in Cats
Irritant contact dermatitis and allergic contact dermatitis are two different conditions discussed together because they produce similar reactions. Both are caused by contact with a chemical. In contact dermatitis, the skin reaction is caused by a direct irritating effect of the chemical. In allergic contact dermatitis, repeated contact produces skin sensitization that results in an allergic response from subsequent exposure. Both types of dermatitis are rare in cats because their haircoat and their grooming habits protect the skin from sustained contact with chemicals. This is especially true for allergic contact dermatitis.
Both irritant and allergic contact dermatitis affect parts of the body where hair is thin or absent-the feet, chin, nose, abdomen, and groin. These areas are also the most likely to come in contact with chemicals. Liquid irritants may affect any part of the body.
Contact dermatitis of either type produces red, itchy bumps along with inflammation of the skin. Scaliness follows, and the hair falls out. Excessive scratching causes skin injury and, secondarily, infected sores. The rash from allergic contact dermatitis may spread beyond the contact area.
Chemicals that can cause irritant dermatitis include acids and alkalis, detergents, solvents, soaps, and petroleum by-products. Substances that can cause an allergic reaction include flea powders, shampoos (particularly those containing iodine), poison ivy, poison oak and other plants, fibers (including wool and synthetics), leather, plastic and rubber food and water dishes, and dyes in carpets. Neomycin, found in many topical medications, can produce an allergic reaction, as can other drugs and medications.
Flea collar dermatitis is a reaction to the insecticide in the collar. It affects the skin around the neck, producing local itching and redness, followed by hair loss and crust formation. This condition may spread to other areas. In addition to causing local hypersensitivity, flea collars may cause toxicity from the absorption of chemicals, especially if there is contact between the collar and broken skin or open sores. Litter box dermatitis, in which the cat is allergic to the litter being used or an additive in the litter, affects the feet, the skin around the tail, and the anus.
Treatment: Consider the area of exposure and try to identify the skin allergen or chemical causing the problem. Prevent exposure. Topical or oral corticosteroids or antihistamines, prescribed by your veterinarian, can help to reduce itching and inflammation. They do not cure the problem. Allergyshots and immune therapy may control the symptoms but do not cure the problem.
If an irritant substance gets on your cat, bathing immediately may minimize or even eliminate any symptoms.
This article is excerpted from “Cat Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.
Copyright © 2008 by Delbert Carlson, DVM, and James M. Giffin, MD. All rights reserved.