Flea Infestation and Flea Prevention in Dogs

Published on
Last updated on
8 min read

Key takeaways

Fleas are parasitic insects that live on dogs’ and other animals’ skin and eat the blood of their hosts.

  • Fleas are found worldwide in temperate areas
  • Fleas can jump easily between animals and from animals to people, and can bite within minutes of landing
  • Fleas are a public health risk to humans because they are the vector for infectious agents
  • Fleas expose dogs to tapeworm and infectious disease, and can cause anemia
  • Eliminating an established flea infestation is difficult and takes at least 3 months
  • Flea saliva is the trigger for flea allergy dermatitis, the most common allergic skin disease of dogs
  • Many dogs with fleas show no symptoms, but symptoms of flea infestation may include itching, scratching, rubbing, irritation, and restlessness
  • It is recommended that all dogs stay on veterinarian-approved flea prevention year-round
  • Always consult a veterinarian before choosing external parasite control. Many available products are toxic to pets, especially cats.
Are you concerned?

Connect with a vet to get more information about your pet’s health.

Book an online vet

A closer look: Flea Infestation and Flea Prevention in Dogs

Fleas are small, blood-sucking parasites found outdoors worldwide. Fleas infest many types of animals, including dogs. Fleas can transmit diseases to their mammalian hosts, including humans.

Fleas are ubiquitous in many environments, so external parasite control is recommended year round for all dogs and pets that share living space with outdoor animals. Flea infestations may take months to resolve and professional pest-elimination services may be necessary to treat homes and yards in heavily infested areas.

The sooner fleas are found and treated, the less damage they do, so it is important to check a dog’s skin regularly for signs of infestation. Finding a flea on a dog is not an emergency, but it is an immediate call to action.

Connect with a vet to get more information

With DVM, ICH certifications and great reviews by pet parents like you for this symptom

Risk factors

All dogs are at risk of exposure to fleas. Dogs that are not treated with flea prevention, and those with access to wildlife, are at greater risk of flea infestation.

If undetected, or if a dog has an underlying predisposition, severe flea infestation may result in generalized symptoms of flea-borne illness and/or anemia due to blood loss.

Flea-borne illness is a common complication of flea infestation. In particular, fleas are known to transmit tapeworms to dogs. These parasites are also associated with the most common form of allergic reaction in pets: flea allergy dermatitis, which can lead to discomfort and recurring skin infections.

Possible causes

A full-scale flea infestation is caused by a lack of (or inadequate) preventive parasite control. Dogs may be exposed to fleas at any time, but it is not likely to develop into a larger problem if preventative measures are already in place.

Main symptoms

Many dogs with fleas show no symptoms at all.

Flea dirt appears as small black specks on the skin or in the bedding. To distinguish flea dirt from regular dirt, wet it: flea dirt (the blood of its host) turns reddish-brown. Many pet parents discover their dog has a flea problem when they bathe the dog and see blood swirling in the water.

Dogs who are allergic to flea saliva develop a severely itchy rash, called flea allergy dermatitis (FAD).

Testing and diagnosis

Diagnosis of flea infestation is straightforward. Veterinarians look for evidence of fleas on dogs’ fur during a complete physical exam. Failure to find fleas does not rule out their presence.

If secondary symptoms of flea-borne illness, anemia, tapeworms, or flea allergy have developed, additional diagnostics may be necessary.

Steps to Recovery

Once a flea infestation is confirmed, the challenge is killing all the eggs, larvae, and fleas in the dog’s environment, including beds, bedding, carpets, furniture, vehicles, and yard.

Safe and effective pesticides are an important part of flea treatment and prevention. Many flea-control products available over the counter are unsafe, even when used as directed. Cats are particularly sensitive to pesticides. It is important to notify a veterinarian of all animals living in the home when discussing options for parasite control.

In order to successfully eliminate an existing flea population, the selected pesticides must be:

  • Used on every pet in the household
  • Correctly applied on time and administered exactly as directed
  • Used for at least three months, and sometimes even longer

If indicated, your vet may also recommend environmental pesticide treatment, either with a proven safe and effective spray or by contracting a professional service.

In the house, yard, and car, the goal is to break the life cycle by removing as many immature fleas as possible. Regular vacuuming and laundering is necessary to remove eggs and fleas from the home as they hatch. Flea larvae thrive on protected substrates like carpet and away from high-traffic areas.

Flea infestation will last as long as preventive treatment is not in place for all animals in the household. Once treatment has begun, it may take up to three months to fully break the flea life cycle and end the infestation.


It is recommended that all dogs stay on veterinarian-approved flea prevention year-round. Even with preventive measures in place, it is important to check dogs’ skin regularly for any sign of fleas or flea dirt to prevent widespread infestation.

Always consult a veterinarian before choosing external parasite control. Many available products are toxic to pets, especially cats.

Environmental management outdoors may also help reduce flea populations pets are exposed to. Making the yard less inviting to wildlife and other animals can help minimize exposure to fleas.

Outdoor management strategies include

  • Install a solid fence
  • Increase sunlight to the yard by trimming trees; eliminate as much shade as possible
  • Mow the grass regularly, keep bushes cut short, and clear leaf litter and organic debris from under bushes and in flower beds
  • Do not put yard clippings and trimmings in the compost pile
  • Spread cedar chips where the dog lies regularly. Fleas don’t like the smell
  • Buy nematodes (small worms that eat insect larvae) from the local garden center and sprinkle in the lawn and other areas
  • Avoid overwatering the lawn and garden
  • Regularly spray an approved insecticide in places like dog houses, gardens, flower beds, and shady places like under porches and decks. Always follow the directions on pesticides, keeping pets away from recently treated areas until it is safe to re-enter the environment
  • Prevent access to areas where wild animals with fleas might go like crawl spaces, cool hidden corners, and garbage storage areas
  • Discourage wildlife: install bright lights, play loud music, put up barriers, and leave cider vinegar soaked rags around until they move on

A note about “natural” flea-control products: an abundance of pesticide-free products claiming to kill, prevent, or repel fleas are available on the market. There are no natural products currently on the market backed by scientific evidence supporting their safety nor their efficacy in preventing or eliminating fleas.

Is Flea Infestation and Flea Prevention in Dogs common?

Fleas are the most common external parasite reported in dogs.

Typical Treatment

  • Preventative pesticide
  • Environmental controls
  • Antiparasitics, anti-inflammatories, or antibiotics for secondary complications

Our editorial committee

Our medical review team is responsible for validating and maintaining the quality of our medical information.