Fleas are the most common external parasite in dogs, and they cause intense itching and often hair loss or skin infections. They can also carry different diseases that may affect dogs and people. 

Year-round flea preventative products are crucial for keeping fleas off our pets. Because most of the flea population lives in the environment, successful flea treatment must also focus on interrupting the fleas’ life cycle in the home and yard.  

Transmission and life cycle  

Fleas prefer warm, ambient temperatures and moderate humidity, which makes inside the home a prime environment to thrive. There are four stages in the fleas’ 3-week life cycle: egg, larva, pupa and adult. Adult fleas live on animals, while the other stages are found in the environment.  

Each female flea lays about 40 eggs per day on animals’ skin, and these eggs can easily roll off into the surrounding environment. Larvae hatch from eggs and seek dark, warm areas such as carpet fibers, where they form a cocoon and become pupae. Pupae can remain undisturbed for months and cannot be killed with insecticides, freezing or drying.  

Adults emerge from cocoons when they sense that a potential host is nearby, by detecting vibrations, light or carbon dioxide. Since adult fleas prefer not to leave a host once they find one, dogs generally get fleas after being in an environment with newly emerging adult fleas, rather than by making direct contact with another dog with fleas. 

Clinical signs 

The severity of symptoms will depend on the extent of flea infestation, as well as the size and age of the host animal. The most common clinical signs of fleas include: 

  • Itching, biting or over-grooming  

  • Hairless or redness to skin — on the back near the tail, as well as in between or on the back of the animal’s legs  

  • Small red bumps or flaking skin, if infection occurs (flea allergy dermatitis) 


Fleas can be diagnosed either by identifying adult fleas, flea dirt (feces) or patterns of flea allergy.  

However, fleas will not always be seen. Patterns of flea allergy include redness, hairlessness or itching on the back near the tail and the back of thighs.  


Your veterinarian may need to provide medications for skin or tapeworm infections, itch relief or anemia depending on the severity.  

The goal of flea treatment is to interrupt the flea life cycle on the animal and in the environment, which may take a few months to completely manage. This is achieved by: 

  • Treating all pets routinely with appropriate flea products.   

    • Some options available over the counter include topicals or long-acting collars. 

    • Oral preventatives require a veterinary prescription.  

    • Your veterinarian can help you choose the most effective product for your pet.  

  • Wash all bedding and vacuum frequently (to trigger the release of pupae) followed by use of a spray intended to kill adult fleas quickly and stop their reproduction. Remove pets from the area prior to use.   

  • Remove leaf or brush piles outdoors, and consider spray treatment of any shaded areas, such as under decks, flower beds or anywhere that pets frequent.  

  • Multiple treatments will be needed at set frequencies to interrupt the life cycles. Professional exterminators may also be used.  


Fleas are species-specific, meaning that they prefer to live on dogs, but people can also be bitten by fleas in the environment and get small, red, itchy spots.  

Fleas can carry different diseases which could affect both pets and people, such as tapeworms or even plague. 


Fleas can be an ongoing frustration if the life cycle of the flea and the environmental management is not managed adequately — and it may take several months to completely gain control of the environment.  

However, flea preventatives for pets are very effective, accessible and easy to use. That being said, dogs with flea allergies will remain very sensitive to flea bites, and even very minimal exposure can cause a reaction.  


  • Maintain year-round, consistent flea prevention for all pets in the household 

  • Manage the home  

    • Vacuum frequently indoors  

    • Wash pets’ bedding regularly 

  • Manage the yard  

    • Remove leaf or brush piles 

    • Keep the lawn cut short 

    • Store food and garbage properly to keep rodents away 

Learn more about flea and tick prevention