How to Spot the Signs of Fleas

Reviewed by Amy Flowers, DVM on May 14, 2023
akita dog getting bath

The problem begins with some scratching here and there. Maybe you spot some tiny specks around the house that you might’ve missed before. Maybe that beautiful hair that was so thick is looking a tad thin these days. Before you know it … yep. It’s confirmed.

Fido has fleas. And you’d better check Fluffy the Cat, too.

More than 2,500 different species of fleas exist throughout the world, yet one is the most common among American dogs and cats. It’s called Ctenocephalides felis, or the cat flea.

That’s right. If your dog has fleas, they’re most likely cat fleas.

Every pet owner should be aware of the signs of a possible flea infestation. They include:

Your dog (or cat) is scratching. Even if you don’t catch fleas red-handed, if you see your pet scratching or biting at its fur, fleas may well be the culprit. That’s because not only can fleas cause a sharp pain when they bite, their salivary glands give off a substance that's irritating to many dogs and cats.

You can see them. Adult fleas are about an eighth of an inch long. They’re reddish-brown and very thin. It’s hard to really see what they look like without a microscope (though it’s easier on a light-colored fur), but they do have big back legs. They can jump, by some measurements, upward and outward at least 12 inches in a single leap. And one estimation finds that for every adult flea found on your pet, there are at least 100 immature ones hanging around.

You can see what they leave behind. It’s called “flea dirt,” and it looks a little like pepper. You can spot it on your pet’s skin, or your pet could leave it someplace, like:

  • Its bedding
  • The carpet
  • That favorite chair they have been sleeping on even though you’ve ushered them off it a thousand times

The specks are actually bits of dried blood that will turn from black, to brown, and finally back to red if you rehydrate them on a wet paper towel.

You can see other suspicious stuff around your home: Fleas lay eggs on your pet -- tiny white ovals -- that mostly fall off into the environment around it (your bed, the dog bed, the carpet, that favorite chair), only to hatch a few days later into flea larvae.

You can see larvae, too. They're little, squiggly, worm-looking things with brown heads that will feed on all those specks until they wrap themselves up into a cocoon called a pupa. From larva to pupa takes about 3-4 weeks. After that, they’re fully grown fleas, looking for a ride and a little of your pet’s (or your) blood.

If you see tapeworms -- internal parasites that are white or pinkish white and look like small pieces of rice that often show up by slipping out of your pet’s rectum -- that’s a sign your pet may have been having it out with fleas. Tapeworms happen when your pet ingests a flea carrying the tapeworm eggs.

Your dog (or cat) is losing its hair: It’s not from the fleas themselves, but from all the itching and biting. Fleas often gather at the neck and shoulder blades of your pets. The base of the tail and along the back of the legs is a favorite hangout for them, too. Those are also places animals will bite to get to the fleas. That can take its toll on a pet’s coat. With full-blown infestations, fleas are visible in the bare areas of a pet’s belly, too.

Their skin looks irritated: If you can get past your pet’s fur and look at the skin, fleabites are usually small, raised red dots. Again, look for bites on the back and neck and on the base of the tail. Another problem with fleabites is they can lead to flea allergy dermatitis, also known as fleabite hypersensitivity. If your pet has this, their skin can become itchy, red, and scaly. It can lead to secondary skin infections, too.

Their gums are pale: With a large infestation of fleas, some pets (especially smaller kittens or pups) could be in danger of anemia, or a loss of red blood cells. Fleas can take in up to 15 times their body weight in blood. Pale gums often signal anemia.

Fleas are, in the strictest sense of the word, pests. But they can be way more than that. They can transmit disease (to humans, too) and cause life-threatening problems for your pet. If you see any signs of fleas, ask your veterinarian what to do.

Show Sources


Purdue University: “Medical Entomology, Insects and Ticks: Fleas.”

Penn State College of Agricultural Sciences, Department of Entomology: “Fleas.”

The Ohio State University, College of Food, Agricultural, and Environmental Sciences, Department of Entomology: “Cat Fleas.”

American Kennel Club: “What do Flea Bites Look Like on Dogs?”

American Society for the Prevention of Cruelty to Animals: “Fleas and Ticks.”

University of California-Davis Veterinary Medicine: “Fact Sheets: What About Allergies?”

Texas A&M University Texas Agricultural Extension Service: “Controlling Fleas.”

American Kennel Club: “Anemia in Dogs.”

Wilkerson, M., Veterinary Immunology and Immunopathology, Dec. 28, 2003.

University of California Agricultural & Natural Resources, Statewide Integrated Pest Management Program: “Fleas.”

CDC: “Fleas.”

Dobler, G., Parasit Vectors, published online July 11, 2011.

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