Atopy is a hypersensitivity reaction to inhaled allergens that likely has a genetic component. Allergens such as pollen, mold, and house dust mites often cause allergic humans to sneeze. In cats, the primary sign seen is pruritus (itching).

Most cats with inhalant allergies have evidence of skin disease. The skin may be red and have raised crusty lesions. Pruritus manifests itself as excessive grooming, chewing and scratching. Some cats are not observed scratching but symmetrical hair loss is noted. The head, ears, neck, and ventral abdomen are commonly involved.

These same lesions may be seen with many other skin diseases. Some of the more common are flea allergies, food allergies, skin fungal infections (ringworm) and skin parasites. Testing to rule out these other causes of itching must be done before a diagnosis of atopy can be made. Fleas are the most common cause of itching in cats. Flea treatment must be applied to all cats that are evaluated for atopy. Tests such as skin scrapings or biopsies, fecal flotation, Wood’s lamp evaluation, fungal cultures and an elimination diet for three to eight weeks help rule out other disorders.

When the clinical signs of allergy are seasonal and limited to less than three months, oral medication may be adequate to keep the cat comfortable. It is important to recognize that these medications control itching but do not eliminate the condition. Chlorpheniramine and prednisolone are the medications most commonly used for cats. They are both given at the lowest possible dose that will control clinical signs. Other medications that might also be used include omega 3 fatty acids and cyclosporine.

If the clinical signs last longer than three months, the cat does not respond to therapy or if the medications are contraindicated, other options must be explored. Referral to a veterinary dermatologist for intradermal skin testing and hyposensitization therapy should be considered.

Management is usually life-long and the multifaceted therapy involves:

Environmental Control

1. Reduce exposure to offending allergens by removing them from the environment if possible.

2. Use HEPA air filters to reduce pollens, molds, and dust in the home.

3. Use humidifiers and/or dehumidifiers to maintain a home humidity of around 30%.

Flea Control

1. Use monthly flea control on all pets to prevent flea bites from increasing the pruritis.

2. Treat any secondary skin and ear infections with appropriate therapies for 2-4 weeks.

3. Control pruritis (itching) with systemic glucorticoids, antihistamines, and essential fatty acid supplements as needed.

By following this management plan, the uncomfortable signs of allergic dermatitis can be controlled.