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Fleas on Dogs: What to Look For

With nearly 2,000 species and subspecies, fleas thrive in warm, humid environments, and feed on the blood of their hosts. Dogs play host to the cat flea (Ctenocephalides felis), whose dark brown or black body is usually one to three millimeters in length.

Why Are Dogs Susceptible to Fleas?

Fleas are hearty and nimble, and when searching for a host, they can jump 10,000 times in a row (the length of three football fields). Three pairs of legs make for excellent leaping capabilities (up to two feet), and a laterally flattened body allows for quick movement in a dog's fur.

With a complete life cycle ranging anywhere from 16 days to 21 months, depending on environmental conditions, fleas are most commonly found on a dog's abdomen, the base of the tail and the head. With heavy infestations, however, fleas can thrive anywhere on the body. They feed once every day or two, and generally remain on their host during the interim.

What Are Some Signs of Fleas in Dogs?

  • Droppings or “flea dirt” in a dog's coat
  • Flea eggs on dog or in dog's environment
  • Allergic dermatitis
  • Excessive scratching, licking or biting at skin
  • Hair loss
  • Scabs and hot spots
  • Pale gums
  • Tapeworms

What Are Some Complications of Fleas in Dogs?

Since fleas can consume 15 times their own body weight in blood, they can cause anemia or a significant amount of blood loss over time. This is especially problematic in young puppies, where an inadequate number of red blood cells can be life-threatening to some dogs. Signs of parasitic anemia include pale gums, cold body temperature and listlessness.

When a dog has a heightened sensitivity to the saliva of fleas, just one bite of a flea can cause an allergic reaction. This condition is known as flea allergy dermatitis and causes intense itching and discomfort for your dog. Signs include generalized hair loss, reddened skin, scabs and hot spots. Flea allergy dermatitis often leads to skin infections.