I. The Flea

Almost everyone who owns a pet knows what a flea is, and most have seen fleas. The flea which infests both dogs and cats is the cat flea, known as Ctenocephalides felis.

The cat flea

Adult fleas live both on a dog and in its environment, but prefer to live on the dog. Adult fleas must spend some time on a dog or other host in order to eat. Their food source is blood, obtained by biting the host. Fleas lay eggs on a host, but the eggs easily fall off into the environment. In the environment, the eggs will hatch and develop into new adult fleas. This process can take as little as two weeks, or as long as six months depending on the conditions in the environment. Warmer and more humid conditions promote quicker development of fleas. Not only can fleas cause skin disease in many animals, including man, but also they are also carriers of tapeworms, and the bacterium that causes the Plague, Yersinia pestis. Female fleas can eat up to fifteen times their body weight in blood per day. A flea infestation can cause enough blood loss to kill young or sick animals.

II. What is Flea Allergy Dermatitis?

When a flea needs to feed, it finds a host, such as a dog, and bites it. When the flea bites the dog, compounds in the flea saliva are released into the dog’s skin. These compounds stimulate an allergic reaction. The result of this allergic reaction is extreme itchiness or pruritis. Flea Allergy Dermatitis can occur in dogs as young as six months old, but may not appear until a dog is older than six or seven years.

III. Symptoms

The main symptom of flea allergy dermatitis is severe itching which is worst in the area where the tail joins the body (base of the tail), around the rear legs, and on the belly near the hips. Other symptoms that also occur in this area and include:

• Hair loss


• Scabs or crusts on the skin


• Small bumps or pustules on the skin (pimples)


• Redness of the skin


• Thickening and darkening of the skin if the problems are chronic

Sometimes flea feces (known as flea dirt) and adult fleas are seen on the dog; however, it is not unusual to find no fleas or flea dirt. Many dogs with Flea Allergy Dermatitis are so allergic to fleas that only one or two bites are needed to make them extremely itchy and the one or two fleas that caused the problem are never found.

IV. Diagnosis

If a dog is very allergic to flea bites, it may be difficult to diagnose Flea Allergy Dermatitis. Fleas may never be seen on that dog. Frequently, the location of the symptoms and skin lesions will be specific enough that a diagnosis can be made based on that. If not, other diagnostic tests will be needed to rule out other diseases which might cause the same symptoms. These include:·

• Skin scrapings to rule out mange.


• Hypoallergenic food trials to rule out food allergies.


• Skin or blood testing to rule out seasonal or inhalant allergies

V. Treatment and Prevention

The mainstay in treating flea allergy dermatitis is controlling the flea population on and around the dog. There are many new and effective products available for dogs that will help prevent them from getting fleas. One or a combination of products may be needed to achieve adequate flea control. The following video demostrates how to correctly apply topical flea control products.

It is also important to treat the house and yard that the dog is living in. This will help to prevent the dog from coming into contact with any fleas. The following video discusses the importance of envirnomental control of fleas.

Any other pets that are in the household also need to be treated for fleas.Until the fleas are under control, and when a dog has flare-ups, itching can be controlled with a combination of corticosteroids, antihistamines, and omega-3 fatty acid supplements. Anti-itch shampoos and conditioners can sometimes provide very temporary relief from symptoms as well.

The information in this article is not intended to provide a diagnosis or treatment for your pet and is not a substitute for examination and appropriate treatment by your veterinarian