The adult flea may remain in the cocoon for up to 5 months, but when stimulated by a passing animal the adult can emerge within seconds. Animal and human health Fleas can be a source of both irritation and disease. Dogs and cats scratch constantly when heavily infested, resulting in soiled and roughened coats and, sometimes, in nervous conditions. The most serious effects occur when a pet develops an allergy to flea bites. As few as one or two bites can cause severe itching and scratching in allergic pets.
Cat fleas are the most common fleas on dogs and cats.
They also infest raccoons, oppossums and coyotes. Flea life cycle. Cat fleas do not normally live on humans, but do bite people who handle infested animals. Flea bites cause small, red, itchy bumps, usually on the ankles and lower legs. People with allergies to flea bites suffer from hives, rashes or generalized itching.