As winter approaches and temperatures fall, you may think that you can give your pet a break from their tick and flea medication. But not so fast — many dogs are at risk for ticks and fleas year-round.

Illustration of a dog laying on a rug and scratching itself.

Not only can fleas find their way into your home during the cooler and colder months (typically hitching a ride on the backs of mice and rodents that head into homes for warmth as the winter approaches), but many tick species can survive – and even be active and thrive – throughout the winter, too. Of course, some of this depends on where you live and travel to with your dog, but most regions of the country are affected. And with increasingly warmer winters[1], this is truly no time to let your guard down.

Take the Bite out of Mosquitoes and Heartworms
Fleas, Ticks, & Heartworms
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Winter Pet Safety Tips
Winter Pet Safety Tips

Is Tick and Flea Medication Necessary in the Winter?

Yes. Though many species of ticks and fleas are slowed down or dormant during the winter, certain areas of the United States are not cold enough to truly kill these parasites and stop their activity. Because ticks and fleas can carry diseases that could harm your dog, it’s best to keep them protected all year long.

Risks of Ticks in the Winter

Specific ticks, like the blacklegged ticks in the south, western blacklegged ticks along the west coast, and brown dog ticks in the southern half of the United States, can live and even remain active all winter.

Gulf Coast Ticks, which can transmit tick paralysis, can be active in temperatures as low as 39.2 degrees Fahrenheit[2]. That means that in many parts of the United States, it’s not cold enough to stop tick activity. This tick’s range is expanding beyond the Gulf Coast states.

It’s best to keep your dog on tick and flea preventive medication year-round since you never know when a thaw will be warm enough to allow ticks to be active again.

Risks of Fleas in the Winter

In mild climates, fleas can be a year-round nuisance for your dog, since it never gets cold enough for them to go dormant. In colder climates, fleas can survive in warmer areas like barns, animal dens, or in and under homes. All it takes is one mild day for fleas to become active again.

After major wet weather events, such as hurricanes, fleas are very common. Additionally, if you plan on traveling during the winter with your dog, you may be traveling to a region where ticks and fleas remain active year-round. If you live in an area that can be affected by these weather patterns (or are traveling to one), it’s important to keep your pet on flea medication to keep them protected from the diseases that fleas carry.


Georgette Wilson, DVM

Born and raised in New York City, Dr. Georgette Wilson received her BA from the University of Pennsylvania and DVM from Cornell College of Veterinary Medicine in Ithaca, NY. Dr. Wilson completed a one-year small animal internship at the University of Tennessee. She practiced in the greater New York City area for 11 years prior to entering the veterinary pharmaceutical industry. Dr. Wilson is currently the Zoetis Petcare HQ Medical Lead for the Diagnostics Rapids Tests. In her spare time, Dr. Wilson enjoys travel with her family.

Important Safety Information: Simparica is for use only in dogs, 6 months of age and older. Simparica may cause abnormal neurologic signs such as tremors, unsteadiness, and/or seizures. Simparica has not been evaluated in dogs that are pregnant, breeding or lactating. Simparica has been safely used in dogs treated with commonly prescribed vaccines, parasiticides and other medications. The most frequently reported adverse reactions were vomiting and diarrhea. See full Prescribing Information.

  1. Warming winters across the United States. Accessed October 9, 2019.
  2. Duffy DC, Campbell SR. Ambient air temperature as a predictor of activity of adult Ixodes scapularis (Acari:Ixodidae). J Med Entomol 31:178-180 (1994).