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 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. Allergic reactions usually appear 12 to 24 hours after a bite, and may last a week or more. Fleas that have fed on rodents may transmit diseases, including plague and murine typhus. For this reason, avoid close contact with wild rodents such as squirrels, rats and prairie dogs. Their fleas can bite you and may transmit disease.