Flea Bite Allergy

Have you ever wondered why some pets can have fleas and not be bothered by them, whereas some have severe itchiness and discomfort from just one or two fleas? This is because some cats and dogs are allergic to flea bites whilst other are not. For nonallergic animals, a flea bite will cause only mild and brief itchiness at the site of the bite, whereas allergic animals will react with severe itching anywhere on the body.  Skin conditions due to flea bite allergies are very common, and the problem will worsen with continuous exposure to fleas, leading to hair loss and skin infections with near-constant itching. Just one or two bites a week can trigger the allergy and continue the cycle. There is no specific age for flea bite allergies, but they tend to develop at a young age, normally at about 1 to 5 years old.

Veterinarians diagnose the disease from the symptoms, typical appearance of the skin and coat, and the presence of fleas. The diagnosis is further confirmed from the improvement of the symptoms once treatment is commenced. Usually evidence of fleas is found, either as adult fleas, “flea-dirt” (reddish-brown flea excrement) or white flea eggs. In some cases, fleas are not found as the allergy can be triggered by only one or two fleas that have been dislodged due to scratching. In this case diagnosis is based on the response to treatment, or if need be, by skin testing.

The symptoms in dogs consist of scratching and skin damage due to the scratching and can vary from mild to very severe. Generally skin changes can be seen on the lower back, around the tail, hind legs and belly, but can sometimes affect the entire body. Hair loss, redness, scratches, scabs and abrasions are common, and the skin can become moist and infected from the excessive chewing and licking.  Cats can have similar symptoms, but more commonly they have small bumps and scabs around the head, ears and belly, or inside the hind legs. Excessive licking due to itchiness can cause symmetric hair loss, which can sometimes be the only symptom visible.

Treatment consists mainly of flea prevention, both for the pet and the immediate environment. Flea collars or washes alone are usually not effective, but there are many medications available, normally either oral products or topical (applied to the skin) lotions or sprays. For cats, only use products licensed for cats, as some dog products can be toxic. Never spray your animals with insect repellent products that are meant for the household only – many of these are toxic to animals. All pets in the house should be treated even if only one has symptoms. Sometimes antibiotics are needed to treat bacterial skin infections, and your veterinarian might also prescribe short-term anti-inflammatory medication to control the itching. In some very severe and rare cases the medication has to be continued long-term to ensure the welfare of the animal, but this can be associated with negative side effects. As the allergy can be triggered by a single bite, it is important to continue the anti-flea control medication as long as there is any risk of flea bites.


Article by Dr. Laura Wessman

KSPCA Volunteer

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