Allergy - Flea Allergy Dermatitis in Dogs

My dog's skin has always been itchy and every summer he has to be treated. After a recent series of tests and I was told that he has flea allergy dermatitis. The problem is that I have never seen a flea on him. Is this diagnosis correct?

Flea allergy dermatitis (FAD) is the leading cause of allergic conditions in dogs. In an allergic reaction, the immune system overreacts and produces antibodies to a substance that it would normally tolerate or in an attempt to fight infection.

Flea allergy dermatitis (FAD) is the leading cause of itching in dogs. Adult fleas must bite a dog and obtain a blood meal in order to reproduce. Fleas typically don’t remain on the dog except for the minutes to hours when they are feeding. This is why dog owners often don’t see live fleas on their dog unless there is a severe flea infestation in their immediate environment. When fleas feed, they inject a small amount of saliva into the skin. It is the proteins in the saliva that cause an intensely itchy response to sensitive dogs.

Dogs with FAD do not have to be infested with fleas to be itchy. In fact, a single fleabite can cause itching for several days.

Are only certain dogs allergic to fleas?

FAD can affect any adult dog older than one year of age. Many cases of FAD appear between age one and three in most dogs.

How is flea allergy dermatitis diagnosed?

Clinical signs often give the first clue that your pet may suffer from FAD. Itching and hair loss in the region from the middle of the back to the tail base and down the rear legs (the "flea triangle") is often associated with FAD. Intradermal allergy tests (skin tests) or specialized blood tests (IgE blood tests) can confirm flea allergy in your dog.

What does treatment involve?

Since the injection of flea saliva causes the allergic response, it is important to prevent fleas from biting your dog. Strict flea control is essential. Even though you have not seen fleas on the dog, it’s important to continue rigorous flea treatment and maintain environmental control. Outdoor dogs pose a particular challenge. (For more details, refer to our handout "Flea control".) Modern monthly oral and topical flea preventives are an essential part of good pet parenting for all dogs and cats.

What about desensitization?

Desensitization, or administering "allergy injections," involves injecting increasing doses of a diluted flea antigen over a prolonged period. In some cases, these allergy injections may be required for the pet's life. Desensitization therapy is successful in approximately half of FAD cases.

It is important not to confuse desensitization therapy with corticosteroid or “cortisone” injections to relieve the symptoms of an acute FAD flare-up.

What about steroids or other drugs?

Corticosteroids, "cortisone" or "steroids" are widely used to treat acute episodes of particularly itchy FAD. They often bring about almost miraculous relief from the itching. However, there are significant potential side effects to steroid use. The long-term use of corticosteroids can ultimately result in more harm than good and cause serious, irreversible illnesses. Steroids can be safely used for short-term relief while flea control is being implemented. Combining corticosteroids with antihistamines and/or omega-fatty acid supplements is an ideal regimen for many patients. The goal is to use the lowest dosage of corticosteroids as possible, as infrequently as possible, preferably on an alternating- or every third-day basis. If your dog has developed a secondary bacterial skin infection because of the scratching, antibiotics may also be necessary.

Your veterinarian will discuss the pros and cons of the various treatments for FAD with you during the examination, and will recommend the safest and most effective treatment plan for your pet's individual needs. Prevention is essential and relatively simple and inexpensive. Ask your veterinarian for the best flea preventive for your pet’s lifestyle and needs.