Flea Bite Hypersensitivity in Dogs

Flea Bite Hypersensitivity in Dogs - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

What is Flea Bite Hypersensitivity?

Flea bite hypersensitivity, also called flea allergy dermatitis (FAD) is the most common skin disease of dogs in the United States. According to studies, there are more than 15 antigens present in the saliva of a flea of which can cause an allergic response in your dog if she is sensitive to it. While flea control has improved, flea bite allergies and dermatitis are a common issue, with studies showing that up to 40% of dogs in a particular area will test positive for an allergy to flea bites.

Those dogs that are not allergic will usually not develop lesions from the bites, though they may bite or scratch at the flea as it bites them. Since dogs do not become desensitized to flea bites after an allergy develops, you will want to do your best to prevent them from being bitten by fleas. It does not appear that a particular breed or gender of dog is more likely to be allergic.

Flea bite hypersensitivity can be seen in any adult dog that is over one year of age, with many cases occurring between ages one and three.

Flea bite hypersensitivity occurs when your dog has a reaction to flea bites, experiencing itchiness and redness of the skin.

Symptoms of Flea Bite Hypersensitivity in Dogs

Symptoms of a flea bite allergy appear to be worse in the summer and fall, which are peak flea times. Should your dog have a flea allergy, you will see her bite at the base of her tail and scratch herself often and with intensity. In many cases, there will be a loss or thinning of hair above the base of the tail. Fleas themselves or their feces are often found on your dog, though if you bathe your dog often this may not be the case. In a severe case, your dog can itch all over her body, experience generalized hair loss and display red, inflamed skin. You may also observe hot spots when your dog is having a flea allergy.

  • Intense scratching
  • Hair loss
  • Presence of flea feces
  • Inflamed skin


Some dogs are extremely hypersensitive to flea bites. In these dogs, they may be completely free of fleas as a result of self-grooming excessively. Because of the self-grooming, it may be difficult to find the presence of fleas or feces on your dog. A fine-toothed flea comb (32 teeth/inch) can be used to find fleas and their feces and you can also look closely at your dog’s bedding for eggs, larvae and feces.

Causes of Flea Bite Hypersensitivity in Dogs

Should your dog have flea bite hypersensitivity, she does not have to be infested with fleas to experience significant itchiness; only one flea bite can cause itchiness for a few days.

Diagnosis of Flea Bite Hypersensitivity in Dogs

Should you notice that your dog is scratching herself more than usual, you may consider a trip to the veterinarian so that she may be examined and receive some relief. Your veterinarian will ask you for information the symptoms you have observed and when you first noticed them. He will conduct a full physical examination of your dog; allergies to flea bites can be diagnosed through the observation of symptoms and in some cases the presence of fleas. Intradermal skin testing has been found to be effective in diagnosing a flea allergy, along with specialized blood tests (IgE blood tests).

Treatment of Flea Bite Hypersensitivity in Dogs

When treating flea bite hypersensitivity, your veterinarian will recommend both topical and oral medications that are able to be used for the control of fleas. An adulticide will eliminate the adult fleas, and an insect growth regulator (IGR) will help eliminate immature forms of the flea. This means that they will not reach adulthood and bite your dog in the future. Your veterinarian will take into consideration how severe your dog’s allergy is, how often she goes outside and willingness of your dog to let you treat her when making a recommendation on treatment. Allergy injections, also known as desensitization, may be helpful though are found to be successful in about half of those dogs with flea bite hypersensitivity. Corticosteroids can be used as they will greatly relieve the itching your dog is experiencing. Since there are major possible side effects, your veterinarian may not consider them the best option for your dog. 

You will also want to treat your dog’s environment, to include the indoor and outdoor areas where your dog spends time, particularly the areas where she sleeps. While you may not see symptoms in other pets, you will want to treat them as well, so that they don’t bring fleas around the dog that is allergic.

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Recovery of Flea Bite Hypersensitivity in Dogs

Monthly products are available (both oral and topical) that will be helpful in preventing fleas from impacting your dog. Should your dog develop a secondary bacterial skin infection as a result of scratching, your veterinarian may recommend antibiotics. You will then want to keep an eye on the infection to be sure that it is resolved. Once your dog has recovered, you will want to maintain a flea control program to avoid future infestation and allergic reaction.

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