December 05, 2019

Fleas are tiny blood-sucking parasites that can live on the skin of dogs and other animals. Fleas can cause health problems when they infest your dog, and they can even infest your home or yard which makes it difficult to break their life cycle. What happens when your dog has fleas? How do you prevent them, and what is the best way to treat them?

Understanding the life cycle of fleas

It is important to understand the flea life cycle in order to help with treatment and prevention. Adult fleas will lay eggs after they’ve had a blood meal from your dog, and they can lay up to 40 eggs per day. These eggs will fall off of your dog as he walks and moves, and they will hatch within a few days provided that the surrounding environment is favorable, i.e. warm and humid. It may take a couple of weeks for flea eggs to hatch if the environment is dry or cooler.

Once an egg hatches, the flea is now in the larval stage. These larvae will feed off of what is known as flea dirt, or adult flea feces which looks like little pepper granules on your pet. Larvae will develop over several weeks until they spin a cocoon around themselves, initiating the start of the pupal stage. The cocoon surrounding a pupa is sticky so it can be difficult to remove from carpeting, and the cocoon itself can protect the pupa from chemicals.

Pupae can remain in their cocoons for several days before an adult flea emerges. However, pupae can also remain in their cocoons for many months while waiting for conditions to become favorable. Vibrations, body heat, and dogs walking through the house can all trigger an adult flea to emerge from the cocoon. New adult fleas will start to feed within the first few hours, and they can breed and lay eggs after the first three to four days.  

How can I tell if my dog has fleas?

If your dog has fleas, then you might notice him scratching himself more frequently, and the itching is usually caused by the fleas actively biting your dog. He may also appear restless and uncomfortable.

Adult fleas are easy to detect on dogs with light-colored hair coats but may be more difficult to visualize on darker-colored coats, so you will need to part your dog’s fur to look at his skin or use a flea comb to look for fleas. In some cases, you may also find flea dirt which looks like small curly pepper granules.

Over time, your dog may begin to lose fur and develop bald patches over his lower back. He can also develop a skin infection as a result of frequent biting, licking, and scratching. Dogs can also have allergies to flea bites and develop intense itching and redness as a result. In cases of severe infestations, your dog can become anemic due to the blood loss from flea bites. This is especially dangerous in young puppies and small breed dogs.

Fleas can carry a parasite called tapeworm that can invade your dog’s digestive tract when your dog eats and swallows a flea. The tapeworm sheds eggs by releasing small egg-containing segments that are shed in your dog’s stool. If you see a small yellow or white segment in your dog’s stool that looks like a grain of rice, then it is possible that your dog has fleas as well as tapeworm.

How to get rid of fleas on my dog

There are several methods to help get rid of fleas. Oral medications are some of the most effective ways to get rid of them. A fast-acting oral treatment like Capstar is available over the counter and is great for getting rid of adult fleas quickly. However, it only works for up to 24 hours and does not kill larvae or eggs. Some of the topical OTC products like Frontline and Advantage are effective against all parts of the flea life cycle. Many of the oral and topical prescription flea treatments that are available from your veterinarian are very effective, work quickly, and cover all parts of the flea life cycle. Treatments like Bravecto are long-acting because they last for up to 12 weeks and are also effective against ticks.  

Some dogs may be too young for prescription treatments, or you may not be able to get to your veterinarian right away. In these scenarios, you can bathe your dog with flea shampoo, making sure to scrub every inch of them but avoid contact with eyes. If you plan on using a topical flea treatment, then you will need to wait 24 to 48 hours after bathing your dog before applying the product. If you bathe your dog with flea shampoo after applying a product, then the product will be stripped away.

Topical flea sprays can also help, especially if they are sprayed on your dog’s bedding and around doorways and windows. This is because fleas can infest your home if they are present in your yard, and they can come in from pets who go outdoors, including cats. Flea collars are useful for their repellent properties, but you will want to make sure that your dog also receives one of the topical or oral products mentioned above. Be sure to ask your veterinarian for more information on these products.

Preventing fleas on my dog

Year-round use of an effective flea product is critical. It is easy to assume that your dog won’t pick up fleas because he is only outdoors for a few minutes to go to the bathroom, or maybe he is kept strictly indoors. The fact is that fleas can get in through our doorways and jump on our clothing, and so it is possible for all homes to become infested with fleas. Year-round prevention for all of your dogs and cats is the best way to prevent fleas. Other methods include vacuuming your rugs and carpets routinely, washing your dog’s bedding often, and treating your yard with flea sprays.


Fleas can be difficult to get rid of because it can take weeks or even months to break their life cycle completely. This is why prevention is so important. If you suspect that your dog has fleas, then make sure to contact your veterinarian as soon as possible. She will be able to determine if your dog needs more than just flea treatments, and she will be able to recommend the best products available for flea prevention. You can also help your dog by checking him for fleas at least once a week.


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Meet the Author

Dr. Erica Irish

Dr. Erica Irish

Erica has worked in the veterinary field since 2006, starting out as a veterinary technician before graduating from the UF College of Veterinary Medicine in 2013. As a general practitioner in an animal hospital, she has many interests and is especially interested in dermatology, cardiology, internal and integrative medicine.