Glossary

Flea

A tiny blood-feeding insect that lives on cats, causes itching and allergy, and carries tapeworm and other infections.

Also called: fleas, cat flea, Ctenocephalides felis, flea infestation, flea dirt

The cat flea is a small, wingless, jumping insect that feeds on blood. It is the most common flea on both cats and dogs. An adult flea spends its life on the pet, but the eggs drop off into carpets, bedding and cracks in floors, where larvae and pupae develop. Only a small share of a flea population is visible on the cat at any time, which is why an infestation can last for months.

Signs include scratching, over-grooming, small scabs, and black specks in the coat called flea dirt, which turn reddish when wet. Some cats are allergic and react badly to a few bites, see flea allergy dermatitis. Fleas carry the tapeworm parasite and the bacterium behind cat scratch disease, and heavy infestations can cause anemia in kittens and small or ill cats. Fleas also bite people.

Control means treating every pet in the home and the surroundings, and it takes weeks of repeated effort. Use only products made for cats. Some dog flea products contain permethrin, which is toxic to cats, and a cat can be poisoned by contact with a treated dog. Ask your vet which product suits your cat's age, weight and health, and what to do about the house.

Last reviewed November 7, 2026

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Related terms

Flea allergy dermatitis An itchy skin disease caused by an allergic reaction to flea saliva, where even a few bites trigger scabs and hair loss. Tapeworm A flat intestinal parasite that cats usually catch by swallowing an infected flea or eating prey, seen as rice-like segments near the tail. Cat scratch disease A bacterial infection people can get from a cat's scratch or bite, carried by cats that usually look healthy. Anemia A shortage of red blood cells or hemoglobin, which leaves a cat weak and pale and always has an underlying cause. Ear mites Tiny surface parasites that live in a cat's ear canal and cause itching and dark, crumbly debris.

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