Human fleas lack the conspicuous combs of bristles found on or near the head of cat fleas. They suck blood from humans and a number of other animals, causing sometimes severe itching. The larvae develop on their parents’ feces of partially digested blood and on detritus from the host.
Cat fleas are a common nuisance in homes. When the adults bite and suck blood, they can cause flea allergy dermatitis in humans and other animals. The severity of the allergic response varies, depending on the sensitivity of the host. Cat fleas are intermediate hosts to an intestinal parasite, the dog tapeworm. They are found on both cats and dogs in North America, and they are the most common domestic flea in the United States.