Be FAD-Conscious: What You Should Know about Flea Allergy Dermatitis

We all know that fleas, being the parasites that they are, can cause a lot of complications to our pet. But do you know that the most common skin disease in dogs is caused by fleas too? Flea Allergy Dermatitis (FAD) or hypersensitivity to flea bites affects our canine friends and is also one of the major causes of dermatitis in cats.

FAD begins with the bite of a flea. When the flea's saliva-containing a variety of amino acids, aromatic compounds, enzymes, and other chemicals of various sizes-enters the animal, it induces allergic reactions. The next thing pet owners know is that their pets are infected with the disease.


Most often, dogs with FAD exhibit the following clinical signs:

  • They exhibit intense pruritus or itching that spreads over the entire body.
  • They experience skin rash and develop hair loss on the lower back, tailhead, hinder part and inner thighs. They may also be sensitive in the abdomen, neck and ears.
  • Aside from itching, dogs with FAD are generally uncomfortable and restless. They spend a lot of time scratching, rubbing, chewing, licking, and nibbling their skin.
  • Too much licking can cause their skin to be scaly, stained brown, and hyperpigmented.
  • They may also develop an odor due to chronic itching and secondary infections.

In cats, FAD also manifests itself through itching, repeated licking, scratching and chewing. Cats may suffer from miliary dermatitis, which is characterized by 'blackheads' and hair loss along their back line.


The disease is determined by a number of factors-the animal's history, age, clinical signs, presence or distribution of fleas, and results of test.

In making the diagnosis, one has to consider if it is the flea season or not since most cases of FAD occur in late summer, which coincides with the peak of the flea season. Age of onset is also crucial because the clinical signs of FAD are uncommon in pets less than 6 months of age. Generally, dogs manifest signs of the disease between one and three years of age. Meanwhile, due to excessive grooming activity, some pets may have very few fleas on them at a certain time but it does not mean that they are entirely free from flea allergies.

Part of the diagnosis is to determine and examine the presence of fleas and their excrements that may be seen in the skin of animals. Visual observation can be done initially. However, for an accurate diagnosis, it is highly suggested to ask the veterinarian to do an intradermal skin test, which requires the pet to be sedated lightly in order to inject allergen into its skin, detecting flea allergies.

Treatment, Maintenance and Prevention

The first step to stop flea allergy dermatitis is to eliminate flea infestation. Pet owners can choose from a lot of flea treatment options. They can use fast-acting spot-on products such as Advantage, Frontline or Revolution and oral medication like Sentinel. Flea shampoos, sprays, powder, and other types of flea medicines can also be used. The veterinarian can prescribe the appropriate treatment for one's pet.

Once the pet is treated, it is equally necessary to rid the environment of these pets. Proper sanitation and spraying of insecticide in your surroundings can help. These will prevent fleas from infesting the pet again.

For more information on FAD, check out the Petcyclopedia article by Dr. Sally Gardiner.


Merck Veterinary Manual website. "Fleas and Flea Allergy Dermatitis: Introduction." Accessed: April 11, 2008.

Sousa, Candace A. DVM. "Fleas, flea allergy, and flea control, a review." Dermatology Online Journal 3(2): 7; Accessed:; April 11, 2008