Flea Allergy Dermatitis (FAD) in Dogs

Flea allergy dermatitis (FAD) occurs when the dog has an allergic reaction to the saliva that is injected by the flea under the skin when it feeds.

What are the signs of FAD?

An allergic reaction means that the dog’s immune system overreacts to the flea saliva, resulting in a severe inflammatory response and intense itchiness. The dog will scratch and bite excessively and this self-trauma can lead to hair loss, open sores or scabs, redness of the skin and a scaly haircoat. A secondary bacterial infection can occur which worsens the condition. Most dogs are affected along the back near the tail base, but signs can occur all over the body.

What is the treatment for FAD?

Flea control is the basis of treatment. All fleas must be removed from the dog and its environment, including other household pets. Cats are often overlooked as the source of fleas, especially if they are not scratching themselves.

There are many safe and effective flea products available for killing fleas, and for preventing fleas from reinfesting your dog. Then you need to kill fleas and the other stages of the flea life cycle in the environment. This means flea-bombing areas in the house that the dog can access, treating kennels, baskets, or bedding, and identifying outdoor areas that fleas may exist. This may mean blocking off access to under the house, and using outdoor flea products in places like sandpits or favourite resting areas.

Many dogs will require short-term relief for itching while flea control is started. Corticosteroids are often used to block the allergic reaction and stop itchiness. Antibiotics may be required for secondary bacterial infections. Medicated shampoos are often useful for treating bacterial skin conditions, and for soothing inflamed, itchy skin.

What if my dog is still itchy despite flea control?

If signs persist despite the above treatment, then either there is a breakdown somewhere in the flea control and fleas are still able to bite your dog, or your dog has allergies to other substances. The latter is a common problem, as allergic dogs often have multiple allergies, including pollens and house dust mites (inhalant allergy) and food ingredients (food allergy).

Consultation with your veterinarian will be aimed at decreasing your dog’s exposure to the allergens, control of symptoms and possibly a vaccine which desensitises your dog to the effects of the allergens. A skin specialist can develop this hyposensitisation vaccine after a skin test, although the results are variable.