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Flea Bite Pet Allergies: Can Flea Bites Cause Allergies in Dogs? 

Flea saliva can cause allergic reactions in sensitive dogs, commonly in the form of flea allergy dermatitis. Flea bites can also cause your dog intense itching and discomfort. The diagnosis of flea bite allergy is based on symptoms or skin and blood tests. The best treatment for this type of allergy is to prevent fleas from biting in the first place.

All pet owners have had a flea problem at least once. If you have a dog, you have to deal with the issue of fleas and the allergies they cause.

Some dogs are more sensitive than others, so not all dogs are allergic to flea bites.

Symptoms begin immediately after the dog has been bitten by a flea. Red spots form on the skin from the moment the allergy starts. These are accompanied by extreme itching and will cause your dog to scratch intensely.

Flea saliva is the culprit for triggering allergies.

Tests are usually not required to confirm flea allergy dermatitis, as it can be diagnosed based on an accurate physical examination.

If your dog is sensitive to flea bites, the best treatment is regular flea prevention.

What Does a Flea Bite on a Dog Look Like?

A flea bite looks like a small red or discolored bump on your dog’s skin. They are smaller than usual insect bites and can occur in a straight line or group. A halo can appear around them.

When fleas bite your dog to feed on blood, they inject saliva at the bite site. This saliva is irritating to dogs, and small red bumps can appear at the feeding site.

Flea bites typically appear as a small red or discolored swelling, which can be surrounded by a faded halo. They can become inflamed and infected if your dog scratches intensely.

Allergic reactions to flea bites can occur if your dog is sensitive to the components in their saliva. In this situation, you will notice large, red, and inflamed areas on your pet’s skin.

The daily scratching you see your dog doing when it has fleas is not the same as in a flea allergy. A dog with a flea allergy scratches intensely for long periods.

Fleas are commonly found in many places on dogs:

  • Their Groin
  • The base of the tail
  • On the neck
  • Under the chin
  • In the armpits
  • Between the shoulder blades

The spots where fleas like to feed most often are the warm areas. This is where they feel protected, such as in the groin area and the armpits.

Related: Flea Bites on Dogs: Identification & Symptoms

What Does a Flea Bite on a Dog Look Like

Can Dogs Be Allergic to Fleas?

Some dogs are allergic to flea bites. More precisely, they are allergic to the components in fleas’ saliva. Flea allergy affects dogs of all ages but especially dogs up to five years old. There is no predisposition to sex or breed.

When a dog is allergic, its body reacts to certain molecules called allergens. These allergens can come from a variety of sources, including flea saliva.

An allergic dog can develop skin problems and itching. If your dog is allergic to insect bites, swelling occurs following a bite. Your dog can have an intense itching sensation all over its body.

Allergic dogs often bite their paws until they become inflamed and irritated. Paws are the only part of the body with sweat glands, and they can become inflamed in case of allergy.

Dogs with allergies can develop the following symptoms:

  • Chewing their paws
  • Rubbing their face against the carpet
  • Frequent scratching – some dogs can auto-mutilate
  • Excessive hair loss
  • Irritated and traumatized skin

The components in flea saliva that can trigger an allergic reaction are proteins. Flea bites can result in multiple days of itching for dogs. Although flea bite allergy has no predisposition of breed, sex, or age, it is usually seen in dogs up to five years old.

How Can I Tell If My Dog Is Allergic to Flea Bites?

The symptoms of flea bite allergy are much more pronounced than those of other bites. Your dog can itch and scratch all day long, have large, red, inflamed areas on its skin, and lose its hair.

Most of the time, the only symptoms that can be seen in a dog with flea bite allergy are extreme itching and intense scratching.

Dogs allergic to flea bites can also develop hives or rashes, which can occur on large areas of the body. 

A characteristic area for flea bite allergy is from the middle of the back to the base of the tail and down on the hind legs (also called “the fleas’ triangle”). Hair loss often occurs in this area when a dog is allergic to flea bites due to intense scratching.

To confirm the diagnosis, your veterinarian may perform additional tests, such as skin or blood tests.

How Can I Tell If My Dog Is Allergic to Flea Bites

What Is Flea Allergy Dermatitis?

Flea allergy dermatitis is the most common condition caused by flea bites in dogs and cats. It is caused by the injection of proteins from the flea’s saliva when the flea feeds on an animal’s blood.

More than 90% of fleas on cats and dogs are of the Ctenocephalides felis flea species; these are also the ones that can cause allergic dermatitis.[1]

Flea saliva contains 15 potentially allergenic agents that have a complete antigenic structure.[2]

Non-allergenic dogs tolerate fleas and develop no clinical manifestations in their saliva, while hypersensitivity reactions can occur in other pets.

What Is Flea Allergy Dermatitis
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What Are the Signs of Flea Allergy Dermatitis?

The first sign of flea allergy dermatitis is Itching. The most affected areas are the base of the tail, lumbosacral region, flanks, groin, back of the ears, armpits, or torso. Without careful supervision and care, the injuries can evolve into severe complications due to excessive licking and scratching.

Flea allergy dermatitis frequently occurs in dogs aged 3-5 years. In mild forms, the dermatitis is manifested through reddening of the skin and intense scratching.

In severe cases, a dog can show:

  • Itchy lesions and long-term scratching
  • Crusts and papules (skin tags and bumps mainly found on the lower back, the tip of the tail, and caudal and inner thighs)
  • Erythema (reddening of the skin)
  • Hairless areas (mainly seen on the lumbosacral area, ventral part of the abdomen, and base of the tail)

The diagnosis of flea allergy dermatitis is based primarily on symptoms and secondly on fleas or flea feces. Flea droppings’ presence confirms the existence of fleas. The feces contain digested blood which can be analyzed.

In massive infestations, the diagnosis is obvious, but there are pets in which the allergy is induced by 1-2 fleas.[3] 

In these cases, the diagnosis becomes a little more complicated, requiring intradermal[4] and blood tests.

Common Symptoms of Flea Bites on Dogs

Flea Allergy Dermatitis Treatment

Being a flea-induced medical condition, the first step is to apply antiparasitic substances to your pet. A procedure that usually solves the problem. 

If skin lesions have occurred, a local treatment should also be applied.

In situations where the allergic reaction is intense, a general treatment is recommended, besides the local therapy. This usually consists of the administration of antibiotics, antifungal, and/or anti-inflammatory drugs by the veterinarian. 

The vet may also recommend a hypoallergenic diet for your dog.

Related: Why Is My Dog Itching After Flea & Tick Treatment?

Flea Allergy Dermatitis Prevention

Prevention of flea allergy dermatitis is achieved by using antiparasitic substances on your dog regularly and insecticides in places the dog often hangs around:

  • Garden
  • Cage
  • Carrier

You can also regularly wash its dog bed and blanket as they can contain eggs, larvae, or fleas.

Given that fleas are present all year round, do not neglect to apply antiparasitic substances in cold seasons.

Flea Allergy Dermatitis Prevention
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How to Prevent Fleas on Dogs

You can prevent fleas by applying antiparasitic substances. It is also recommended to disinfect the places where the dog sleeps, plays, and sits around.

There are a variety of antiparasitic products on the market that can prevent fleas on your dog:

  • Spot-on pipettes
  • Antiparasitic collars
  • Antiparasitic shampoos
  • Powders
  • Sprays
  • Tablets

Vets recommend applying antiparasitic products every month during the summer. This should preferably be a combination of products, such as a pipette and collar.

During the winter, the application should be done once every three months.

Spot-on pipettes are the most widely used antiparasitic products. Their dose is calculated based on the weight and age of the dog. 

Always follow the package leaflet and use products that are suited for your dog’s weight. Otherwise, you risk intoxicating your pet.

To apply the pipette, split your dog’s hair on the back of its neck and squeeze out the content directly onto its skin. The product is also to be applied at the base of the tail for large breeds. 

The dog must not be able to lick or groom the area.

Do not bathe your dog 48 hours before and after applying antiparasitic products. The water will wash away the substance, and the product will have no effect.

If your dog stays in the yard, apply an insecticide here. The same goes for apartments. This is done to destroy fleas that have fallen off the dog as well as larvae and eggs.

You can also cut the grass in your yard often and plant as many herbs as possible to keep fleas away. Do not let your lawn fill with dead leaves, especially in shady areas where the humidity is higher.


Prevent fleas by regularly using antiparasitic substances on your dog. By doing so, you will also prevent flea allergy dermatitis.

Flea allergy dermatitis can cause rash, hives, hair loss, and intense scratching, licking, and biting at various areas of the body. Pay attention to your dog’s behavioral changes if it has already come in contact with a flea and act as soon as possible.

Seek the advice of your veterinarian before making any decisions regarding your dog.

About Iulia Mihai (DVM)

Dr. Iulia is a certified veterinarian with more than 10 years of experience in the field. With extensive knowledge of diet, care, and medication, she helps Misfit Animals provide readers with accurate knowledge on technical topics.

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