Irritant contact dermatitis is
caused by the direct effect of a chemical or irritant on the skin. It occurs in areas where
the skin is not well protected by hair, such as the feet, chin, nose, hocks,
stifles, and the undersurface of the body, including the scrotum. Irritant
contact dermatitis can occur after a single exposure or repeated exposure.
Irritant contact dermatitis produces itchy red bumps and inflammation of the
skin. You may notice moist, weepy spots, blisters, and crusts. The skin becomes
rough and scaly and hair is lost. Excessive scratching damages the skin and
sets the stage for secondary pyoderma.
The itchy skin diseases in this table are characterized by
constant scratching, biting at the skin, and rubbing up against objects to
relieve the itch.
Allergic contact dermatitis: Same as contact
dermatitis, but rash may spread beyond the area of contact. Requires
repeated or continuous exposure to allergen (such as wearing a flea
atopy: Severe itching that occurs in young dogs and begins in late
summer and fall. Caused by seasonal pollens. Occurs in mixed breeds...
Chemicals that can cause irritant dermatitis include acids and alkalis,
detergents, solvents, soaps, and petroleum byproducts.
Less commonly, the skin becomes sensitized to a certain chemical and a
delayed type of hypersensitivity reaction develops. This is allergic contact
dermatitis.This rash is indistinguishable from that of irritant contact
dermatitis, but appears after repeated exposure and often spreads beyond the
site of contact.
Allergic contact dermatitis can be caused by chemicals found in soaps, flea
collars, shampoos, wool and synthetic fibers, leather, plastic and rubber
dishes, grasses and pollens, insecticides, petrolatum, paint, carpet dyes, and
rubber and wood preservatives. Chemicals used to clean your carpet are a
frequent source of irritation. Neomycin, found in many topical medications, can
produce allergic contact dermatitis, as can other drugs and medications.
Plastic and rubber food dish dermatitis affects the nose and lips.
Flea collar dermatitis isan allergic contact dermatitis. The signs include
itching, redness, hair loss, and the development
of excoriations, scabs, and crusts beneath the collar. It can be prevented to
some degree by airing the collar for 24 hours and applying the collar loosely.
The flea collar should fit so that you can get at least two fingers beneath the
ring. However, if your dog develops flea collar
dermatitis, the best course of action is not to use a flea collar.
Treatment: Consider the area of involvement and identify the chemical or
skin allergen causing the problem. Prevent further exposure. Treat infected
skin with a topical antibiotic ointment such as triple antibiotic. Topical and
oral corticosteroids prescribed by your veterinarian can relieve itching and
WebMD Veterinary Reference from "Dog Owner's Home Veterinary Handbook"