A pet's itchiness can be due to irritation and allergy, including that caused by flea bites. However, many pet owners may suffer flea denial, assuming that fleas cannot be the source of the problem. Some people may associate fleas with poor pet hygiene, but the cleanest pet, even pets kept indoors all the time, can suffer flea bites and flea allergies.

Dr. Karen Campbell, veterinary dermatologist at the University of Illinois Veterinary Teaching Hospital in Urbana, explains there are many reasons pet owners may assume their itchy pet can't have fleas. "Often owners will tell me they've never seen a flea on their pet, but cats and dogs groom themselves well, removing the fleas before anyone sees them."

"It only takes a single flea to cause an allergic reaction," she points out, so a pet doesn't need to be infested with fleas to have seriously itchy, red skin. If a pet develops an allergy to flea saliva, a single bite can cause irritation that can affect a fairly large area of skin.

The flea goes through several stages during its life cycle. The adult flea spends virtually its entire life on its host, where the female adult lays her eggs. These eggs fall off the host into the environment, where they develop into legless but mobile larvae and feed off organic debris in the indoor or outdoor environment. The larvae develop into pupae that are highly resistant to parasiticides and are encapsulated in tough, sticky cocoons. When they hatch into adults, they can leap onto an unsuspecting host.

Some people believe that if their pet stays in the yard, or stays indoors altogether, there's no way they can get fleas. On the contrary, flea larvae can live in the backyard grass, and any life stage can hitch a ride indoors on the shoes, socks, or clothing of family members. Since larvae don't like light, they will burrow deep in carpeting and cracks in floorboards where even the most obsessive vacuuming and cleaning cannot reach.

Although there are many causes of itchy skin and dermatitis, there are some characteristic patterns associated with flea bite allergy. Dogs usually get inflammation on the rump, belly and the insides and backs of the thighs. There may be papules (small bumps) and crust on the skin.

Flea allergy manifests a bit differently in cats; they often get a condition called "miliary dermatitis"--small white spherical lesions that look like millet seeds. A flea-bitten cat gets these lesions on the rump and around the neck, and may have hair loss on the belly from excessively licking at the skin.

Flea allergy can be diagnosed with a physical examination, and a veterinarian may use a special comb to look for evidence of fleas, such as dark flea feces, known as "flea dirt," under the hair. Veterinarians can also perform an intradermal skin allergy test, similar to that performed on humans, to determine which substances an animal reacts to.

The first step in treating a flea allergy is to eliminate the fleas. There are several types of parasiticides on the market, including shampoos, sprays, foams and oral medications. Each product works differently, for example, some medications require a flea to bite before they kill the flea, whereas others kill fleas simply on contact.

Some products even have residual action; parasiticides that get absorbed into the hair shaft get carried into the indoor environment when hairs and skin flakes are shed, killing fleas in carpeting and furniture and sometimes eliminating the need for harsh aerosol pesticides.

To reduce the itching and inflammation, a veterinarian may prescribe and anti-itch or anti-inflammatory medication. Some cases may require antibiotic treatment to prevent secondary bacterial infection of irritated, damaged skin.

To minimize pets' exposure to fleas, Dr. Campbell recommends some simple strategies: cutting grass short will provide less dark space for light-sensitive larvae to hide in, and keeping the yard clean of organic debris provides less food for their survival. Since flea larvae cannot survive dry environments (relative humidity below 50%), a de-humidifier can help control fleas indoors. Dr. Campbell also recommends washing pet's bedding regularly.