Ask the Vet: Feline skin problems pose challenges

Dear Dr. Thompson-

My daughter has a Siamese cat who started hanging around outside her house who she subsequently adopted. She took her to her veterinarian who found a chip and contacted the original owner that had moved away and was glad someone had taken the cat in. She has a lovely personality and loves my daughter's dog. She has a skin allergy and will lick her hot spot on her back just above her tail. She wears an innertube all the time to prevent her licking her hot spot, otherwise she will lick it raw. At one point she even contracted ring worm there. At first the vet thought my daughter's cat had a food allergy, but now the vet believes my daughter's cat is allergic to dust mites. Any thoughts on her condition? Thanks. (Question edited for clarity)

Feline skin problems can be a challenge to diagnose and treat and often require a stepwise approach to establishing the underlying source of allergy. Symptoms of skin allergies, often called atopic dermatitis, can include hair loss, crusts or scabs, recurring ear infections, ulcers around the mouth or irritated skin. Some cats will scratch themselves bloody and raw from the intense itching associated with the allergy.

An allergy to flea bites is by far the most common cause and people will often assume their cat does not have fleas because it stays indoors, or they do not see any evidence of fleas.

Given cats’ fastidious nature, they may groom off any evidence of live fleas or the digested blood fleas leave behind in their feces that looks like little flecks of pepper. The location of the hair loss on your daughter’s cat is highly suggestive of a flea allergy, especially since she was outdoors for a period. Indoor-only cats can become infested from dogs they share a house with as well. Typically, regular flea control medications prescribed by your veterinarian will be needed for a minimum of six to twelve months since fleas can persist in the environment for an extended period of time depending on conditions. Also, if a housemate is infested with fleas, treating all pets in the home will be necessary.

Food allergies are uncommon in cats and require strict food trials in an attempt to eliminate the allergen in the diet. Environmental allergens in our part of the world are typically seasonal and you did not mention the time frame of your daughter’s cat’s allergies. These are usually a diagnosis of exclusion, but skin or blood testing may be indicated if not responding to treatment. Non-seasonal allergies can still be environmental and may include something like dust mites, but those are exceedingly rare.

Many cats with atopic dermatitis will have secondary skin infections that need to be completely cleared in order to determine the level of itchiness that is present. Her veterinarian may use steroids or other drugs that modulate the immune response depending on the diagnosis. However, establishing an accurate diagnosis is a critical first step and while nobody likes the idea of a flea infestation in their home, it is actually the easiest allergy to treat and control with the broad range of highly effective flea medications available. Good luck.