My cat has fleas and I tried using anything short of a bug bomb to get them off the cat and out of the house. However, all previous attempts have failed. Now I stumble on this idea that you can kill fleas using a dehumidifier. Is this true or am I falling victim to the internet?

  • 2
    Good luck, but the first-line treatment is usually spot-ons that interrupt the flea’s lifecycle, ovicidal spray, very frequent and thorough vacuuming, and patience. There’s a dormant stage in the flea’s lifecycle that’s impervious to anything, that the vibrations from the vacuuming awakens and lets you get rid of it. It’s these dormant invincible eggs that cause the fleas to return, so you need to keep up any intervention you’re doing and vacuum for some time after your cat stops scratching.
    – millimoose
    Commented Sep 28, 2017 at 21:45
  • 2
    Apparently 95% of the fleas in your house are non-adults, so an intervention that kills just the adult fleas isn’t enough. You want to attack on all fronts.
    – millimoose
    Commented Sep 28, 2017 at 21:48
  • I have two dogs and zero fleas for over 5 years. No chemical treatments. I run a 70 pint dehumidifier, 24/7, in a 2000 square foot home in the south. Keep the Relative Humidity <45%. It works for me.
    – Jerry
    Commented Nov 13, 2022 at 11:43

4 Answers 4


No, Dehumidifiers do not kill fleas.

The most effective way is to use a topical or oral chew flea product on all pets (excluding reptiles and birds) in the household for a minimum of 3 months. If you live in an apartment/condo building or a hot climate you should treat your pets 12 months of the year. Areas that get snow and stays cold in the winter months the treatment starts from March until December.

Some recommended products are:

  • Advantage Multi
  • Bravecto
  • Revolution (southern USA this product is no longer effective for fleas)

Extra tips:

  • Wash bedding.
  • Vacuum everything daily.
  • Flea comb pets to remove fleas and flea dirt (flea larva eat flea dirt).
  • Bathe your pet to help remove fleas.

Fun flea facts

  • A female can lay 40-50 eggs per day and 50% of these eggs will be female.
  • The female flea begins producing eggs within 24-36 hours after its first blood meal and continues to produce eggs for >100 days if she remains on the host.
  • Fleas carry tapeworm that can be transmitted to your cat once eaten.
  • Fleas can be vectors for infectious organisms, such as Yersinia pestis (aka Plague), Rickettsia spp., Bartonella spp., and hemoplasma (Mycoplasma) spp.

Note When bathing pets do not bathe while on topical flea treatment and wait 2 days before applying a topic flea treatment AFTER a pet has been bathed.


I have been fighting these for a month now. I used a dehumidifier for years and turned it off when I found fleas in it. Do NOT use a dehumidifier to get rid of fleas. They do not care and they will love the water it sucks out of the air. Persistence is the key. Do not give up. Do not give in! Do all the things others have said.

They can stay dormant for up to 8 months until they sense a meal (warm body), so vacuuming is crucial as the vibration from a beater bar gets them going.

  • One more thought, I think the fleas actually crawled through the exhaust tube from the dehumidifier into the dehumidifier... Try to think of everywhere they might hide. I had to remove all paper products, all carpets, paper bags, boxes, keep stuff off the ground, keep vacuuming daily... Good luck and never give up!
    – Dan B
    Commented Jul 26, 2018 at 20:22
  • Since I posted I have learned that a humid environment is ideal for fleas. Running a dehumidifier is helpful as it makes the environment less conducive for the buggers... Just (as stated above) do not use an exhaust tube as the fleas might crawl in it and lay eggs and put a little dawn in the dehumidifier after you drain it as it will keep it clean and if any fleas do get in there they will drown!
    – Dan B
    Commented Aug 30, 2018 at 14:13

I see some people saying you cannot kill fleas with a dehumidifier. You can, but it would be situational. For instance I have an almost entirely open floorplan of 2800sq/ft, and there is NO carpet of any kind in my home because of how many animals I have. I have a dehumidifier rated for 6500sq/ft that can run continuously because it is self draining; but that would take the humidity so low you'd probably have nose bleeds. Almost any bug that enters my home only lasts a few hours. That being said it doesn't really get the adult fleas off of your pets but the larvae cannot survive low humidity. I recently had a completely flea infested rescue at my house. It spread adult fleas to my other animals, and now my animals no longer have fleas after the adults died out. For most homes this wouldn't work.


Theoretically you probably could, as fleas only can live in a certain humidity but you'd have to keep it going for months to years at a time to ensure any dormant flea eggs are good and dead, or alternatively you could also drop the temperature in the house. Cold temperature with dry air may help to kill them faster, but flea egg can lay dormant for a while which is what you got to be worried about, and that's probably where most of your problems come from. Because if even ONE female is left alive to hatch, she can produce millions more (and quickly) all WITHOUT a male. So anything you do has to focus on getting rid of the eggs (like vacuuming, but I'd remove the bag quickly incase they hatch inside and just crawl out) or you have to keep up your flea treatment plan for MONTHS to ensure that any flea eggs finally die because they can't stay dormant forever, just a really long time so that it feels like forever.

For some fool proof method to kill adult fleas, you could try topical treatments or chewable (but NEVER give your cat dog flea treatments, there's a chemical often used for dogs that they have a much higher tolerance for and can kill your cat at the proportion they use for dogs). But I personally shy away from harsh chemicals as what's meant to kill a flea might not be too good for your cat, and also because my cat's had really bad reactions to typical flea treatments. So you could try looking into diatomaceous earth, I've never tried to myself but I've heard its sharp enough to just cut right though an insect's exoskeleton but is natural and perfectly safe for your cat if you just sprinkle it over their fur, but I'd look into that more before trying it cause I'm no expert in how to use it since I've never had to. But no matter what idea you choose or if you've tried them all, the important thing is to remember those eggs. So either spend a lot of time vacuuming to make sure you get every single egg and don't miss one, or keep up the flea treatments for months at a time. Maybe even over a year, just to be sure.

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