What Do Fleas Look Like? How to Identify (and Kill) These Pesky Bugs

Finding adult fleas is just one way to learn your pet has a flea problem. Other ways can include spotting flea eggs, flea dirt or flea bites, as well as symptoms like scratching.

While we wish we could find just a single flea, get rid of it and call it a day, the reality is fleas multiply rapidly. (A female flea can lay up to 50 eggs per day!) One of the keys to putting a stop to fleas is spotting and eliminating flea eggs.

Here’s how to know if what you’ve found are flea eggs:

• They’re incredibly small. Flea eggs are around 0.5mm in length, making them hard to spot with the naked eye.
• They look translucent. Flea eggs are a light, off-white color, making them difficult to see against light-colored surfaces,
• They’re oval-shaped. Flea eggs can look a lot like salt due to their shape, color and size.
• They can be found anywhere. “Fleas lay their eggs on their host animal, but the eggs are not sticky like some parasites, and they can often—and usually—fall off the host,” says Dr. Patrik Holmboe, DVM, and head veterinarian for Cooper Pet Care in Amsterdam, North Holland, Netherlands. “This means they can be found anywhere in the environment, but often where the animal spends time, such as bedding, carpets, or furniture.”

In the flea life cycle, there are two additional stages of development before a flea becomes a egg-laying, blood-sucking adult: larva and pupa. Here’s how to spot them:

• Flea larvae have a tiny, worm-like appearance and are 1-2mm long. Larvae have no legs, are covered in short hairs and are typically an off-white color.
• Flea pupae are 2-3mm long and encased in a silken cocoon, which can be covered in debris from the environment, making them well camouflaged, Holmboe says.

Finding adult fleas is just one way to learn your pet has a flea problem. Other ways can include spotting flea eggs, flea dirt or flea bites, as well as symptoms like scratching.

Where there are fleas, there’s flea dirt … aka flea feces. (Gross, we know!)

Here’s how to know if what you’ve found is flea dirt:

• It looks like, well, dirt. Flea feces is essentially dried blood meal that fleas excrete after they’ve fed on the host. Flea dirt looks like small, dark brown specks or grains, resembling ground black pepper.
• It’s on your pet or in your home. The most common places to find flea dirt are the same places fleas themselves are most commonly found (e.g. on your cat or dog’s bedding, and the furniture).
• It leaves a stain the color of dried blood. “A classic, common way to confirm the presence of flea dirt is to place the suspected specks on a damp, white paper towel,” Holmboe says. “If it is flea dirt, it will dissolve and leave red or brownish stains due to the blood.”

Learn more about flea dirt and if it’s harmful to humans.

Finding adult fleas is just one way to learn your pet has a flea problem. Other ways can include spotting flea eggs, flea dirt or flea bites, as well as symptoms like scratching.

There are different species of fleas—the most common are cat fleas (Ctenocephalides felis) and dog fleas (Ctenocephalides canis), which despite their names can infest both dogs and cats, as well as humans. But both species’ bites look the same, and both can cause similar symptoms of flea-allergy dermatitis (e.g. intense scratching or biting, hair loss, scabs). In some cases, a pet may develop flea anemia with signs of pale gums, lethargy and loss of appetite.

“It's important to note that individual animals—and people—can have varying degrees of reaction to flea bites, with some showing significant allergic responses,” Holmboe says. “Because of this, two animals can have very different symptoms from fleas, even if in the same environment.”