Diagnosis of feline atopy is made by considering the history, physical examination findings and by ruling all other causes
of pruritus. Intradermal allergy testing plus/minus serologic testing should only be used to determine which allergens to
avoid and to include an immunotherapy vaccine. As normal cats can have positive intradermal allergy tests and serologic test
reactions, these tests should not be used alone to diagnose atopy. Intradermal allergy testing is challenging in cats, as
cats usually have weak reactions consisting of flat, erythematous wheals that require experience in their interpretation.
Some atopic cats will have negative intradermal allergy tests and positive serologic test results. The accuracy of serologic
tests in cats has not been proven due to a lack of controlled clinical studies. However, some dermatologists have reported
good clinical responses to hyposensitization vaccines based on serologic testing in atopic cats. The use of serologic tests
(HESKA, VARL) should be considered if atopy is strongly suspected in cats with negative intradermal allergy test results.
Cats should be off oral corticosteroids for at least one month, injectable corticosteroids for six to eight weeks, and antihistamines,
fatty acids and topical corticosteroids including eye and ear medications for two weeks before intradermal allergy testing
or serologic testing to avoid false negatives due to drug interference. Response to hyposensitization in cats is approximately
50-75 percent, depending on the study. Most cats respond within three to six months, with some taking eight to 12 months to
show signs of improvement.
In addition to hyposensitization, antihistamines (see Table 3), omega-3/omega-6 essential fatty acids, hydrocortisone and
oatmeal-containing shampoos/cream rinses, Aveeno oatmeal soaks, Soft Paws® to prevent self-trauma, and topical anti-pruritic
agents (Corticalm lotion®, Relief Spray®) can also be tried to reduce pruritus. For moderately severe cases, oral, ophthalmic
and otic prednisolone, triamcinolone or dexamethasone may be tried, but should be used in combination with the other treatments
listed above to minimize the dose needed (steroid-sparing effect). The lowest possible every other day (prednisolone) and
every three and seven day (triamcinolone, dexamethasone) dose should be used. Cats on long-term corticosteroids should have
periodic physical examinations, blood work, urinalysis, and urine culture performed to screen for diabetes mellitus, urinary
tract infection, and hepatic and renal disease. Cats on chronic corticosteroid therapy are also more prone to demodicosis
and dermatophytosis. For refractory cases, chlorambucil or cyclosporine can be tried, but these drugs are expensive and require
regular laboratory monitoring, and are best prescribed by a dermatologist.
Table 3: Antihistamines Useful in the Treatment of Feline Atopy (only pure antihistamines, without painkillers or decongestants,
should be used to avoid toxicity).
Feline otitis, acne and allergic dermatitis are some of the most common diseases seen in clinical practice. Some cases may
be straightforward, while others can be a real challenge to diagnose and treat. Early, accurate diagnosis of the underlying
problem is essential to successful long-term management of these often chronic conditions. It is essential to follow a logical
and well-organized thought process during the planning of your work-up of these cases. Frequent client communication and patient
re-examinations are very important. Referral to a board-certified dermatologist may be needed in refractory cases in order
to obtain the best possible outcome for your feline patients.