Final answer:
Flea allergic dermatitis (FAD) is a Type I hypersensitivity reaction that triggers an immediate allergic response in pets exposed to flea saliva. Dogs and cats typically do not develop tolerance to flea saliva; rather, they can become more sensitized over time. Managing FAD is crucial and involves the use of flea control products to reduce exposure.
Step-by-step explanation:
Hypersensitivity and Flea Allergic Dermatitis (FAD) in Dogs and Cats
Flea allergic dermatitis (FAD) is an example of a Type I hypersensitivity reaction in dogs and cats, occurring nearly immediately once they are exposed to flea saliva. This allergic reaction is due to an immune response mediated by IgE antibodies. Upon the initial bite and exposure to flea saliva, an allergic pet's immune system reacts by producing IgE, which then primes mast cells to release inflammatory mediators like histamine upon subsequent exposure. This reaction causes discomfort and severe itching in the affected animal. Generally, dogs and cats do not become tolerant to flea saliva; instead, they tend to become more sensitized and react more severely upon repeated exposures.
Unfortunately, this implies that rather than developing tolerance over time, pets with FAD will typically experience increased sensitivity to flea bites, with each subsequent exposure potentially exacerbating the allergic reaction. Pet owners must manage FAD through prevention, typically using flea control products to minimize exposure and thus limit the hypersensitive reaction.
While acquired immunodeficiency (such as from infection) or inherited immunodeficiency can affect the immune system's response, they do not directly result in tolerance to allergens such as flea saliva, which is specifically involved in FAD. Examples of Type I hypersensitivities include allergic responses to food, insect venom, and pollen, all of which involve a similar IgE-mediated mechanism.