Does heat kill fleas?

Summary

Heat does kill fleas. They’ll die in temperatures above 95°F (35°C). Outdoors, fleas die when temperatures rise above 95°F for more than 40 hours a month. In dryers, it’s recommended to use the highest heat setting to kill fleas.

Details

Hot Temperatures Kill Fleas

Adult Fleas

Adult cat fleas can’t survive in temperatures above 95°F (35°C). At this temperature, they’ll die within two days unless relative humidity exceeds 75% Fig 1.

Fig 1 Days it takes (y-axis) for 90% of unfed adult fleas to die at various relative humidity percentages (x-axis) while temperature is kept constant at 95°F.

Flea Eggs & Larvae

Flea eggs die in temperatures above 100.4°F (38°C). In slightly cooler temperatures, 95°F (35°C), 40% of eggs will survive to hatch. However, the eggs will desiccate if relative humidity is less than 75%. And the eggs will die in fully saturated air because heat accumulates within the shells.

Though some eggs may hatch at 95°F, it’s still too hot for the larvae to mature into adults. Around 30% of larvae will live long enough to spin cocoons and complete their pupal-imaginal molt, but 100% of the fleas will die within the cocoon, never to emerge.

Outdoors in Summer

In the summertime, fleas will die outdoors when temperatures exceed 95°F for more than 40 hours a month. In hot climates, fleas will die in structures that trap heat, such as dog houses, cars, or RVs.

In a Dryer

Fleas can’t survive in a dryer. To kill fleas on garments and bedding, it’s recommended to launder the items for ten minutes at 140°F, and then dry at the highest heat setting. Multiple factors will prevent survival, even if the heat somehow doesn’t kill the fleas. The dry conditions will cause desiccation, and the tumbling action will cause physical damage. Plus, the washer’s water and detergent will likely wash away and drown the fleas.

References

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Discussion

  • Karrie Cox July 26, 2016, 4:26 pm

    What smell that fleas don’t like that can kill them?

    • Adam Retzer July 26, 2016, 8:17 pm

      Karrie, I’ve yet to properly research this area.

      Certain botanical compounds from folk-history claim to negatively impact fleas, including fleabane and pulegone. Neem has also been found to be toxic to fleas. That said, I don’t know how efficacious these substances are at repelling or killing fleas.

  • JoAnn November 3, 2016, 9:59 am

    I am having a tough time getting rid of fleas in my home. We don’t have pets so not sure how the gestation began. They have gotten in clothing. We wash them and once we put them in the dryer as one seem to still live. Do they evolve in something else when u spray. I am seeing these small silver shiny thing n my clothes when they come out of the dryer and when it’s cool I have seen them on my skin especially on my face. Can you help.

    • Adam Retzer November 3, 2016, 3:07 pm

      This doesn’t sound like cat fleas (C. felis) to me, of which this site is based on. It may be human fleas (P. irritans). However, based on your description, I would guess these aren’t fleas at all, especially the part about seeing shiny silver things on your clothes and skin. It may be a good idea to get a picture of the pests so they can be properly identified, or get in contact with an exterminator.

  • Loretta Frank June 23, 2017, 9:56 pm

    I’ve got fleas in my garden area, and have sprayed twice with a product recommended by the UCD extension dept here in Woodland, Ca. There are no animals around, and not sure how these came about, or what else to do. When in the garden I have to change shoes and socks and hose off feet and legs good. Don’t want to bring any into the house. I’m reading they can’t survive in hot weather, and we’ve had 5 days over 100 degrees temp. Still have another 2 days predicted. Can you help me?

    • Adam Retzer July 2, 2017, 12:30 pm

      Though fleas can’t survive heat, they may be able to survive in shady outdoors area in hot temperatures. In fact, these are the exact places where they’re found, because it’s where animal hosts often take shelter. The fleas develop in shady, humid, wind-protected areas. Common examples are in dense ground cover, under porches, and vegetation around structures. These are the areas that should get the most attention when you spray. Pyriproxyfen (Nylar) is the best outdoor treatment, according the studies I’ve read.

      Please view our page on Outdoor Flea Sprays for more information. I’ve tried to make it as comprehensive as possible. If you have any questions after reading this page, please let me know.

  • Jane October 13, 2017, 11:17 am

    How long a cycle in the dryer would be recommended for garments that can not go in the washer first (nor wet into the dryer)? Is an hour at 155 degrees long enough to (definitely) kill the eggs and pupae? Two hours? I can’t find anything on a dryer cycle without the washer. Maybe it just doesn’t work on its own?

    Thanks for keeping out this site and all of us informed!

    • Adam Retzer October 17, 2017, 10:37 am

      I don’t have an exact time. However, I would think an hour in the dryer at that temperature would kill any potential fleas. They shouldn’t be able to survive the heat and desiccating conditions.

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