Glossary

Fleas

Tiny blood-feeding insects that cause itching, can trigger allergic skin disease and carry tapeworm, and infest the home as well as the dog.

Also called: flea infestation, flea allergy dermatitis, FAD, flea control, flea bites

Fleas are small, wingless, jumping insects that live on blood. The cat flea is the one most often found on dogs. A flea bite itches, and some dogs are allergic to the saliva, so a single flea can cause intense scratching, hair loss and sores, called flea allergy dermatitis. Fleas also carry tapeworm, and heavy infestations can cause anemia in small puppies.

Adult fleas on the dog make up only a small part of the problem. Most of the life cycle, eggs, larvae and pupae, develops in carpets, bedding and soil, so a home can stay infested for months. Control works best year-round, and for all pets in the household.

Ask a veterinarian to pick a product. Some made for dogs are dangerous to cats, and a product made for another species should never be used.

Last reviewed November 8, 2026

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Related terms

Tapeworm A flat intestinal worm, usually caught by swallowing an infected flea, that sheds rice-like segments seen near a dog's tail. Atopic dermatitis An inherited tendency to develop itchy skin and ear disease from allergens in the environment such as pollen, dust mites and molds. Hot spot A fast-appearing, red, wet and painful patch of skin that a dog creates by licking or scratching, usually because of an underlying irritation. Ticks Blood-feeding arachnids that attach to dogs outdoors and can carry diseases such as Lyme disease, ehrlichiosis and Rocky Mountain spotted fever.