Does Dawn dish soap kill fleas?

Summary

Dawn dish soap does kill fleas. It works by reducing the surface tension of water. Fleas sink and drown instead of remaining on the water’s surface. The dish detergent also prevents insects’ waxy cuticles from repelling water. As a result, water can enter their respiratory system to suffocate them.

Details

Adding dish soap to water is a common way to drown fleas. For instance, placing a plate of soapy water beneath a lamp works as a flea trap. Or fleas can be drowned in a bowl of soapy water after being combed off a pet.

Dawn Works as a Surfactant

Forcing Fleas to Sink

Dawn contains surfactants, which are compounds that lower the surface tension of water. Fleas will sink and drown when a couple drops of Dawn are added to water. Without a surfactant, fleas won’t break the water’s surface tension. This is because of their small size and water-repellent layer of wax. They’ll stay on the surface, flailing around and possibly escaping. Fleas can survive up to seven days in water, and up to 24 hours when submerged.

Allowing Water into the Respiratory System

Insects don’t drown easily. Their respiratory systems are resistant to oxygen deprivation. Fleas, and other insects, are covered in a layer of wax that repels water and makes them non-wettable (hydrophobic). The waxy layer extends into the trachea, preventing water from entering their respiratory systems.

Dawn’s surfactant properties make fleas more wettable. The waxy cuticle won’t repel water, and thus it’ll enter into their respiratory systems. The fleas drown as the water displaces air. In addition, the soap creates suds which may physically block the spiracles (respiratory entries), preventing the exchange of air and causing suffocation.

Bathing Pets with Dawn

Dawn is sometimes used as an alternative to flea shampoos. The detergent drowns fleas on pets by the same mode of action as previously mentioned. However, it’s important to keep in mind that dish soap isn’t made for animals. Dawn is much harsher than pet shampoos. It’ll remove an animal’s natural protective oils, and their skin can get extremely dry and irritated. Even with gentle, pH balanced pet shampoos, it’s advised not to bathe pets more than once a month. Avoid using Dawn on animals with skin infections.

Insecticidal Effect of Soap

Soapy water has been used as an insecticide for thousands of years. It’s believed that soaps break down cell membranes and remove the wax from insect cuticles. As a result, insects can’t retain water and quickly desiccate. Soaps may also interfere with the cellular metabolism of insects, working as growth regulators. However, glycerin soaps show little to no effect on fleas.

References

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Discussion

  • Yolanda August 3, 2016, 8:12 pm

    My dog has been itching excessively what should I do

  • Robin R September 26, 2016, 6:14 pm

    Does generic “Dawn” work as well as the real stuff for killing fleas?

    • Adam Retzer September 27, 2016, 11:14 am

      I’d assume so. All dish soaps should have surfactants in them.

  • Shelley Stone November 8, 2016, 2:43 pm

    Re Puppy Flea Bath- Does it matter which Dawn soap one uses to kill fleas on dogs?

    • Adam Retzer November 9, 2016, 5:59 pm

      It shouldn’t matter which kind of Dawn you use. They should all contain a surfactant ingredient.

  • Ryan D June 2, 2017, 1:53 am

    My cat has a sensitive skin condition where he’s allergic to the flea saliva therefore causing a massive outbreak of irritation to just one bite with some severe flea bites, should I use Dawn, or should I use a flea shampoo with natural ingredients?

    • Adam Retzer June 6, 2017, 5:05 pm

      I’m not a vet, so I can’t give any specific advice. However, I’d opt for a flea shampoo with natural ingredients. Dawn can be harsh on the skin, removing the skin’s natural oils and causing dryness and more irritation.

  • Louine gilliam June 17, 2017, 5:48 am

    I did a flea dip on my dog approx 3 to 4 days ago but he still has fleas, I was told at vets that if I wash him in dawn dish soap It would strip away the dip and I could put his first shield on. Is that correct?

    • Adam Retzer June 19, 2017, 3:12 pm

      Yes, the Dawn dish soap will remove the flea dip. It’s not a good idea to wash the dog after treatment has been applied, especially with Dawn. Flea dip/drops work by incorporating into the dog’s natural oils, which then spread over the dog’s hair and skin. The Dawn will remove the oil and thus the treatment.

      It’s not uncommon to find fleas on pets after treatment has been applied. The treatment should kill the adult fleas on the dog. However, 95-99% of fleas are eggs, larvae and pupae living in the environment. As these immature stages mature into adults, they’ll jump onto the dog. So you are likely seeing new fleas on the dog. These fleas should succumb to the treatment within 12 hours, dying before they can reproduce.

      Give it more time before you deem the flea dip ineffective and look for other control options. If you want to remove the fleas you find on your dog, using a flea comb would be a better option than Dawn.

  • Lisa Rodriguez September 18, 2017, 11:49 pm

    Are they bitting me or do I have the creep claws from see them on the dog.

    • Adam Retzer September 29, 2017, 10:56 am

      If they bit you, then you would know. The bite reaction is similar to a mosquito bite and would be quite itchy the day after the bite.

  • Eileen October 4, 2017, 10:54 am

    Hi all, it’s been a horrible flea season here in the Poconos. We have 3 beautiful little cats who are indoor cats. Yet, they caught fleas. Reading your comments I want to add 2 things we’ve learned. The blue Dawn is the gentlest and recommended. The lavender Dawn actually repels fleas.

  • Lilith November 18, 2017, 3:17 pm

    Can Dawn dish soap be used around the house to kill fleas too? What would be the best way to use Dawn dish soap for around the house flea killing?

    What is the best way to use Dawn dish soap as a flea bath for your pet? Should I start at the head and wash down the body to tail for best results?

    Should I use non concentrated soap or concentrated soap?

    Thank you!

    • Adam Retzer November 19, 2017, 3:35 pm

      Lilith, unfortunately, I don’t have good answers to these questions.

      I suppose Dawn could be used around the home, but I don’t know how effective it would be. Most fleas develop at the base of carpets (or cracks in hard floors). Using Dawn on carpets probably isn’t a good idea, as it will be extremely sudsy and difficult to remove. I’m guessing there’s a good reason why there are shampoos specifically designed for carpets. And even with vacuuming, wet carpet cleaning, and steam cleaning, you won’t be able to kill 100% of the fleas. It seem to me like it could cause more problems than it will solve, but I don’t know for certain.

      Washing from head to tail makes sense to me, as it won’t allow the fleas to escape and hide anywhere.

      I don’t think it matters whether it is concentrated or non-concentrated. In the article I mainly reference non-concentrated Dawn though. The main thing is that it should be a detergent with surfactant properties (which most dish washing soaps should be).

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