ABSTRACT
This chapter discusses basic immunological concepts in the context of actual cases seen in clinics. It discusses in the case of Flea Allergy Dermatitis (FAD). The presence of fleas and the absence of other ectoparasites, with a typical distribution of inflammatory lesions, provides strong suggestive evidence of FAD. Flea allergy dermatitis is a type I and/or type IV hypersensitivity disease of the skin, in which the canine patient produces immunoglobulin E (IgE) antibodies against salivary antigens of the flea. Although the initial immune response to flea salivary antigens is usually an IgE-mediated hypersensitivity, chronic cases of FAD are sometimes associated with a type IV hypersensitivity. Immunotherapy for FAD has been investigated, but this therapy is not commonly used in clinical practice. Immunotherapy for FAD has been investigated, but this therapy is not commonly used in clinical practice. FAD has been cited as the most common allergic disease in the cat.
