Flea Allergies in Dogs (Flea Allergy Dermatitis)

PetMD Editorial
March 01, 2019
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Updated on March 1, 2019

Flea allergy dermatitis (flea allergies in dogs) is the most common skin disease in pets. And although flea allergies in dogs usually develops when dogs are young (less than 1 and up to 5 years of age), a dog flea allergy can begin at any age. It is the saliva from flea bites on dogs that is actually believed to be the cause of the allergy or sensitivity.

The flea life cycle includes the adult flea, egg, larva and pupa. Adult fleas are the ones that bite because they cannot survive long without feeding.

Once the adult flea lays its eggs on the host it will fall off, leaving the eggs to mutate through the rest of their life cycle. This generational process continues on the host pet until the flea population has been eradicated entirely. Once an adult flea loses their host, they cannot survive for very long.

Symptoms of Dog Flea Allergies

Flea allergy dermatitis in dogs usually causes severe itching of the skin. This condition is medically referred to as pruritis.

As few as one or two flea bites on dogs can cause pruritis for a very sensitive dog. Symptoms may persist even after some form of flea control has been used since most flea control for dogs requires the flea to bite to be killed.

Symptoms are often episodic, but most dogs will have symptoms that worsen with age. Some dogs can also suffer behavioral problems as a result of flea bite hypersensitivity, with a condition called neurodermatoses.

Most owners first notice frequent and severe itching and scratching, hair loss, and scabs on the dog's skin.  Typically, dog flea allergies cause these problems on the back half of the dog; however, dogs that are allergic to fleas can have a reaction that causes lesions anywhere on the body.

Importantly, fleas or flea dirt may or may not be visible. Dogs may chew the flea off and swallow it before you ever see the flea.

Diagnosis of Flea Allergies in Dogs

By using a dog flea comb to inspect your dog's hair, you can detect fleas or flea dirt more easily.

Skin tests for mites or bacterial skin diseases may be recommended if fleas cannot be found. Sometimes the best diagnostic method is to just treat for fleas.

Flea Allergy Dermatitis Treatment

Flea control for dogs and prevention are essential for dogs with flea bite hypersensitivity. There are numerous options on the market that kill the adult fleas for a period of time, but all should be repeated (as indicated) for continuous flea control.

Topical dog flea treatments are applied to a small area, usually at the top back of the neck where the dog is unable to lick it off.

Most oral products are prescription flea and tick preventatives that require a veterinary prescription to obtain. Dog flea shampoos are not sufficient for dogs that are allergic to fleas; continuous management with one of the long-term products is essential.

Which Dog Flea and Tick Control Is the Best for Dogs With Flea Allergies?

The most effective flea control for dogs that have flea allergies is one that repels fleas. Permethrin-based products are available as monthly topical treatments (Vectra®, Vectra 3D®) and long-lasting dog flea collars (Seresto®) that offer up to 8 months of protection.

Veterinarian Warning: As these collars have become more popular, there are many forgeries online. Purchase your dog’s permethrin collar from a reputable dealer such as your veterinarian or other known dealer and beware of copycats at low cost.

There are also many pet products that can be used to treat for fleas during their immature stages of life (i.e., eggs). However, if the house or yard has an infestation, environmental treatment will be necessary.

Fleas will bite people too. When flea medications cause them to leave their animal host to search for another host, or when the infestation becomes severe, it can lead to humans becoming the next target. Preventing the flea life cycle in the environment is an important part of flea control for dogs with flea allergies.

Dogs that are allergic to fleas may require steroids or antihistamines to relieve their pruritus if they do become infested. Likewise, if a secondary bacterial infection develops as the result of open sores, dog antibiotics may be prescribed.

Follow-up exams are often necessary to determine how treatments are progressing.

Living and Management

The most important factor in helping a dog with flea allergies is the application of regular doses of flea treatment on a timely basis. Because it takes only one or two flea bites on dogs for an allergic animal to start itching, it is best to be consistent with flea control products.

Your veterinarian may recommend multiple concurrent methods of flea prevention for allergic dogs to prevent discomfort and recurrence of symptoms.

Image: Jaromir Chalabala / Shutterstock