At room temperatures, the entire life cycle may be completed in about 18 days. Fleas may be found on pets throughout the year, but numbers tend to increase dramatically during spring and early summer. The cat flea is suspected of transmitting murine typhus to humans, but its primary importance is in its annoyance to people and pets. Cat fleas readily try to feed on almost any warm-blooded animal. Some people are bothered by the sensation of fleas walking on their skin, but bites are the major nuisance.
Bites tend to be concentrated on the lower legs but can also occur on other parts of the body.
The bite consists of a small, central red spot surrounded by a red halo, usually without excessive swelling. Flea bites usually cause minor itching but may become increasingly irritating to people with sensitive or reactive skin. Some people and pets suffer from flea bite allergic dermatitis, characterized by intense itching, hair loss, reddening of the skin, and secondary infection. Just one bite may initiate an allergic reaction, and itching may persist up to 5 days after the bite. Cat fleas may also serve as intermediary hosts of dog tapeworms.