What parasite commonly lives in a dog’s fur and causes itching?

The story behind the answer

Fleas are the most common external parasite on dogs. These tiny, wingless, blood-feeding insects live in the fur, causing intense itching, scratching, and sometimes hair loss or scabs. Many dogs develop flea allergy dermatitis—an exaggerated skin reaction to flea saliva. A telltale sign is “flea dirt” (black specks of digested blood) that turns reddish-brown when wet.

Remember: fleas are fast jumpers that make many small bites; ticks are slow, engorging arachnids; mites are microscopic and often cause mange; lice are less common and species-specific. Because most of a flea’s life cycle happens off the dog (eggs and larvae in carpets and bedding), effective control means treating the pet and the environment. Fleas can also transmit tapeworms if a dog swallows an infected flea.