by Jody Helmer
You notice something small skitter across the hair on your dog’s back and think, “Was that a flea?” There is a high likelihood that the answer is yes.
Fleas are the most common parasites that affect dogs and cats, with some research showing that 28% of cats and 14% of dogs had infestations.1 But what do fleas look like, and how can you tell if your pet has a flea problem?
What Do Fleas Look Like?
Fleas mature in four stages: egg, larva, pupa and adult insect.2 Here’s what to look for in each stage.
Flea eggs are white, oval-shaped and miniscule, measuring just 1/64 inch long, making them almost impossible to see.3 Although fleas can lay eggs on your pet, the eggs often fall off and land on dog beds, cat perches and other places where your pet spends time.3 It takes 1 to 12 days for flea eggs to hatch.3
Larvae are white and worm-like and can reach up to 5 millimeters in length, making them longer than adult fleas.4 You’re more apt to find larvae in carpet fibers, under leaf litter or in other dark places, but larvae don’t typically live on your pet.4
Fleas remain in the larval stage for 5 to 11 days (but this stage can last up to three weeks) before larvae produce an oval, whitish-colored cocoon and transform into pupae.4 It takes up to two weeks for pupae to develop into adult fleas.4 Similar to larvae, flea pupae tend to be found in carpets or under vegetation, not on animals.4
When adult fleas emerge, the insects find their way onto your pets for a blood meal, and that’s when a flea infestation starts.4 So, just how small are fleas? And what do fleas look like to the human eye?
Adult fleas measure less than one-eighth of an inch in length,3 which is about the size of a poppy seed. Their bodies are dark brown or black and appear flattened on the sides.3 Their backs are equipped with tiny spines that face backward, making it easier for them to anchor to your pet’s fur.3 Adult fleas have six legs and no wings.5
Do Fleas Crawl or Jump?
Fleas don’t have wings, which means they get around by crawling and jumping. Despite their small size, fleas are excellent jumpers and can reach heights 110 times the length of their bodies—which means that cats and dogs of all sizes and all living situations can end up with flea infestations.6
What Do Flea Bites Look Like?
Flea bites create super small, raised red dots on the skin. Since your pet is covered in fur, flea bites can be hard to see. Some dogs and cats are allergic to flea bites; for these pets, even minor flea infestations can cause intense itching. And scratching can cause inflammation, creating larger red areas around the bite.7
What Does Flea Dirt Look Like?
The droppings that fleas leave behind are called flea dirt. These small flecks that resemble black pepper are often the most obvious signs of fleas. Since fleas are so small and move so fast, you may spot flea dirt on your pet’s skin or stuck in their hair before you see any fleas.7
To determine whether your pet has flea dirt, put a few specks on a paper towel and wet it. If the paper towel turns brownish-red, it’s flea dirt.
Symptoms of Flea Infestation
You’ll probably notice the symptoms of fleas before you spot the tiny parasites. In pets, flea infestations can cause:7
Severe scratching (in pets with flea allergies)
Biting and chewing at the skin
Hair loss, especially around the neck, ears, lower back and base of the tail, which are the areas on your pet’s body that fleas prefer
Red, irritated skin
Scabs at the site of the bites
Flea anemia (in severe cases)
Remember: Pets will not itch from their fleas unless they are allergic to flea bites. No scratching does not mean no fleas!
Diagnosing a Flea Infestation
To diagnose a flea infestation, look for the signs. If your pet scratches and bites at their skin frequently, you spot adult fleas or flea dirt, or you notice your pet has red spots on their skin or missing hair, a flea infestation is the likely cause.8 Some pets are excellent at grooming and can hide evidence of fleas, so keep them on preventive medications and make sure your vet checks for fleas during wellness exams.
Treating a Flea Infestation
Fleas can be treated with over-the-counter or prescription products, including oral or topical medications or long-acting flea collars. Your vet might also recommend medications for skin and tapeworm infections that can treat flea diseases that are a result of a flea infestation.8
Always use the medication that was designed for your pet’s species and weight. It’s dangerous to use canine flea and tick medications on cats.
The fact that the majority of the flea life cycle takes place in the environment and not on your pet is one of the reasons fleas can be so difficult to control. It also highlights the importance of treating your environment, not just your pet.
To protect your pets from fleas, you’ll need to treat your home to kill fleas at all stages of development. Wash all bedding and dog beds, and vacuum the carpets with a product intended to kill fleas. Outdoors, remove leaf and brush piles where flea larvae and pupae can hide. Professional exterminators can spray areas where fleas hide.8
Estimated Costs Per Treatment Option
Monthly flea preventive medications cost less than $16 per month for dogs and less than $12 per month for cats.9 Flea collars cost as little as $10 for up to six months of flea protection.10
How to Prevent Flea Infestations
Preventing flea infestations is similar to treating them: Give your pet monthly flea preventives, wash their bedding, vacuum regularly and keep the yard tidy to make it inhospitable to flea larvae and pupae.8
Abdullah, S., Helps, C., Tasker, S. et al. “Pathogens in fleas collected from cats and dogs: distribution and prevalence in the UK.” Parasites & Vectors. https://parasitesandvectors.biomedcentral.com/articles/10.1186/s13071-019-3326-x. Published February 6, 2019. Accessed August 7, 2023.
“How Fleas Spread Disease.” Centers for Disease Control and Prevention. https://www.cdc.gov/fleas/life_cycle_and_hosts.html. Reviewed August 13, 2020. Accessed August 7, 2023.
“Fleas.” University of Maryland Extension. https://extension.umd.edu/resource/fleas. Updated March 1, 2023. Accessed August 7, 2023.
Dryden, M.W. “Fleas in Dogs and Cats.” Merck Veterinary Manual. https://www.merckvetmanual.com/integumentary-system/fleas-and-flea-allergy-dermatitis/fleas-in-dogs-and-cats. Updated October 2022. Accessed August 7, 2023.
“What are fleas?” Michigan State University Extension. www.canr.msu.edu/ipm/uploads/files/Fleas.pdf. Published May 2007. Accessed August 7, 2023.
Berenbaum, M. “Flea-flickers and football fields.” American Entomologist. https://academic.oup.com/ae/article/54/3/132/2474870. Published July 1, 2008. Accessed August 7, 2023.
Burke, A. “What Do Flea Bites Look Like on Dogs?” American Kennel Club. https://www.akc.org/expert-advice/health/flea-bites-on-dogs/. Published March 25, 2022. Accessed August 7, 2023.
Cohen, A. “Fleas.” Cornell University College of Veterinary Medicine. https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/health-info/fleas. Updated December 2, 2022. Accessed August 7, 2023.
“Cutting Pet Care Costs.” ASPCA. https://www.aspca.org/pet-care/general-pet-care/cutting-pet-care-costs. Updated 2021. Accessed August 7, 2023.
“Flea & Tick Collars for Dogs.” PetSmart. https://www.petsmart.com/dog/flea-and-tick/flea-and-tick-collars/?pmin=0.01&srule=price-low-to-high&start=0&sz=24. Accessed August 7, 2023.
by Jody Helmer