Flea allergy dermatitis

The flea allergy - even flea bite allergy, flea saliva allergy, flea allergic dermatitis or allergic flea dermatitis - is caused by the saliva of fleas allergic skin disease that occurs mainly in domestic dogs and domestic cats. Symptom is intense itching, which can lead to self-inflicted severe skin lesions and secondary infections. The treatment is performed by a flea control and prophylaxis, against the itching can temporarily glucocorticoids are used.

Occurrence and pathogenesis

Flea allergies in dogs and cats are a fairly common phenomenon and, in dogs, especially by the cat flea (Ctenocephalides felis ) is triggered. It affects animals of all breeds and ages. Although the disease occurs more frequently in the summer, it occurs throughout the year. Increased disease inclination have dogs that suffer from other allergy, atopic dermatitis: Approximately 80% of atopic dogs develop at a flea allergy flea exposure. A flea allergy occurs even in martens and occasionally in sheep and goats, on, in which case the cat flea is also the most common cause.

As allergy triggers (allergens ) proteins and haptens come from the saliva of the fleas with a molecular mass of 6-58 kDa into consideration. The first identified allergenic flea saliva protein consisting of 158 amino acids was the Cte f 1 ( Cte f is Ctenocephalides felis ) with a molar mass of 18 kDa. A total of at least 15 different flea allergens come as the cause in question, who most frequently reacting a molar mass of 25-58 kDa.

The flea allergy is largely a by immunoglobulin E ( IgE) -mediated type I reaction with degranulation of mast cells and an increase in eosinophils ( eosinophilia). In an experimental study on laboratory mice showed a close relationship between the amount of immunoglobulin E and the degree of clinical disease, with CD4 -positive T - lymphocytes and interleukin -4 were significantly involved in the pathogenesis. In some cases it may also occur a type IV reaction. In addition, other immunological mechanisms are discussed, such as delayed cellular immune response to IgE and hypersensitivity of the skin with immigration basophilic granulocytes and degranulation of these cells by IgE or IgG binding.

Clinical picture

The main symptom of flea allergy in dogs is intense itching, especially in the lumbar, groin and tail area to which the animals gnawing and licking respond. As the first skin lesion ( primary lesion ) occurs in a small papule. Occasionally there is a swelling of the popliteal lymph nodes. By gnawing and licking develop normally more lesions such as erosions and crusts, a so-called "hot spot", a circumscribed, superficial suppurative skin infection ( pyoderma ). Also an overgrowth of Malassezia pachydermatis with skin, a yeast of the natural skin flora is observed more frequently, so that it comes secondary to Malassezia dermatitis. In chronic existence of a flea allergy occur hair loss, hyperpigmentation and skin thickening.

In cats, the clinical picture is variable. Concerned here are primarily the tail and lumbar, abdominal and groin and neck. The main appearance is in addition to itching skin inflammation with large millet seed papules and crusts ( miliary dermatitis). Also hypersensitivity ( hyperesthesia ) of the back may indicate a flea allergy. Longer periods may be patchy or both sides of symmetrical hair loss. Through intensive licking can develop a flat, raised skin redness ( eosinophilic plaque). Even a non- painful canker with immigration of neutrophilic granulocytes and secondary bacterial infection may be an expression of a flea allergy. A flea allergy in cats can also be accompanied by swollen lymph nodes and is clinically not always be distinguished from a non-allergic dermatitis after flea exposure.

In sheep, a flea allergy manifests mainly on the limbs, with martens similar to the clinical picture of the dogs.


In addition to the clinical picture and to erfragenden lack of flea prevention can be detected in the fur using a flea comb fleas or flea dirt. Since fleas are not permanently reside on the host, a negative finding, however, is not diagnostically meaningful. In addition, cats are especially due to its intense grooming able to eliminate fleas quickly. However, since even a single flea bite can trigger an allergy, this sole reference to a flea exposure can be. Another indication is the detection of the eggs of the tapeworm cucumber core in the feces, as this requires fleas as an intermediate host.

An intradermal test with a purified flea saliva protein is suitable for the diagnosis most likely. The sensitivity and specificity is 90% here. Whole body extracts from fleas have too low allergen content and with a sensitivity of 67%, only a limited value. When intradermal test 0.05 ml of a test solution are injected into the skin. After 10 to 20 minutes when positive findings of a wheal, in some animals even after 24 or 48 hours, so that a three-time control of the reaction is indicated. As a positive control histamine is administered at a different location. A previous treatment with glucocorticoids can lead to false negative results. In such a case, the test must be repeated with depot preparations after six weeks of two. Disadvantage of this test is that for him a skin area to be shaved and corresponding test solutions with a limited shelf life should be kept in stock.

The diagnostic accuracy of serological tests of blood samples by ELISA is not without controversy. The sensitivity is 87%, although quite high, the specificity 53%, however, insufficient. But since they are more practical for the vet, these tests are performed more frequently than the intradermal test.

The "gold standard " is considered the provocation test, in which 10 newly hatched, sober and microbiologically safe fleas are recognized on the animal, but this evidence is hardly practical.


The best therapy is a consistent flea control. This can by regular use of long-acting insecticides (eg, fipronil, imidacloprid, lufenuron, Metaflumizone, Nitenpyran or selamectin ) can be realized, which are used therapeutically in an infestation. Case of proven infection should include a treatment of the environment of the animal, especially the berth and preferred staging, done because fleas do not permanently reside on the animal and the effectiveness of the applied on animal drugs is limited to this part of the flea population. The ambient treatment is carried out by regular vacuuming and washing of floors and carpets, supported by a chemical flea control with chlorpyrifos, permethrin, propoxur, fenoxycarb, methoprene or combinations of these agents (eg Bolfo -Plus, Kadox, VetKem ).

From the acute symptoms can be used as anti-inflammatory agents, glucocorticoids such as prednisolone acting briefly twice at an interval of 48 hours ( " two -day - treatment "). In cats Rosje and Willemse recommend a five-day prednisolone. Antihistamines are usually ineffective because the itching is hardly mediated by histamine in dogs and cats.

The previous studies on desensitization showed unsatisfactory results, possibly because they have only been performed with flea whole-body extracts.