Can You Use Dawn Dish Soap to Kill Fleas on Pets?

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PetMD Editorial
Published: May 31, 2019

Reviewed for accuracy on May 31, 2019, by Dr. Katie Grzyb, DVM

You’ve seen the ads where Dawn dish soap is being used to clean wild birds who’ve been impacted by oil spills. If Dawn is effective and gentle enough for wildlife, you may be wondering if it can kill those pesky fleas on your cat or dog, too.

While Dawn dish soap can kill fleas, it’s not the most effective or efficient method, and it won’t prevent flea infestations.

Here’s why Dawn dish soap might not be the miracle flea-killer you’d hoped it would be for your four-legged family member.

How Does Dawn Dish Soap Kill Fleas?

Dawn’s ability to remove grease, grime and oil from wild birds can be attributed to a chemical reaction.

When soapy water is combined with oil or grease, it forms micelles (clusters of soap molecules) that trap the gunk, explains Dr. Chris Reeder, a board-certified veterinary dermatologist with BluePearl Pet Hospital in Franklin, Tennessee.

To kill fleas, a completely different process occurs.

Fleas have exoskeletons that allow them to float in water, explains Dr. Reeder. “Dawn (and other soaps like it) creates a kind of surfactant, or surface tension, that will compromise the exoskeleton and make adult fleas sink,” he says. So essentially, the soap drowns the fleas.

Why Can’t Dawn Dish Soap Control Flea Infestations?

Although Dawn kills fleas, veterinarians say it doesn’t repel them or prevent infestations. Think of it as more of a temporary fix than a permanent solution.

“Since only a small percentage of fleas are on a pet at any given time, fleas from the environment will simply hop right back on and restart the infestation cycle,” says Dr. Jennifer Coates, DVM, a veterinary writer, editor and consultant based in Fort Collins, Colorado.

Plus, flea populations can quickly grow out of control, says Dr. Reeder. “One adult flea can lay up to 50 eggs per day. Even if 10 percent hatch, then that would be five fleas from one female, and the majority [of the hatching fleas] will be female,” he says.

Dawn was not designed to be a flea repellent, let alone one that can control this many fleas for extended periods of time.

Dawn Kills Adult Fleas, But What About the Offspring?

While Dawn dish soap is used primarily to kill adult fleas, says Dr. Reeder, there are three other flea life stages to consider.

“Adult female fleas lay eggs that fall into the environment. Over a period of days, they hatch, and a larval (centipede-looking) form emerges, lasts for a few days, then forms a pupa (or cocoon),” Dr. Reeder says.

The problem with killing just adult fleas that you can see is that you’re not eradicating all those other stages. “Every time your dog or cat is outside and you [bathe them] with the soap product, you’re not doing anything to really reduce the local flea population,” Dr. Reeder explains.

Can Dawn Dish Soap Can Irritate a Pet’s Skin?

Veterinarians also generally don’t recommend using Dawn for fleas because of skin-related issues.

“For example, if the pet already has irritation from having a number of fleas on the skin, and you’re putting Dawn on skin that’s already irritated, there is potential for it to worsen,” says Dr. Reeder.

Dawn is not the best shampoo product for dogs with bacterial skin infections, and it’s not labeled for canine or feline use, he says.

Instead, you should opt for a product designed specifically for pets, says Dr. Reeder.

Should You Ever Use Dawn Dish Soap on Pets?

“We will use Dawn in the rare instance that we have a severely flea-infested kitten or puppy who needs to have the fleas removed immediately. These pets are generally too young to use flea preventatives as recommended by the manufacturer,” says Dr. Susan Jeffrey, a veterinarian at Truesdell Animal Care Hospital in Madison, Wisconsin

If you do use it on young kittens or puppies, she recommends using a very small amount and diluting it with water. “Afterward, I'd use a flea comb to remove any remaining dead and dying fleas,” she says.

Dr. Reeder says pet parents might want to use Dawn if they see a large number of fleas on their adult pet. “They could certainly use that product to help remove the fleas directly from skin and hair coat, and that would be about the only way I would use it,” he says.

Again, this would also only happen in rare cases where your pet may have been exposed to fleas from other pets at places like boarding facilities or pet daycare. You should always keep your pet on year-round flea and tick prevention so they will never become infested in the first place.

You can always be prepared for this scenario in the future by stocking up on over-the-counter Capstar that can rapidly kill all adult fleas on your pet. But just like with Dawn, Capstar is only effective for 24 hours for adult fleas in cases of infestation.

Prescription oral and topical preventatives kill fleas and prevent infestations much more effectively and efficiently.

“Your veterinarian can recommend a safe and effective flea control product based on the specifics of your pet’s health and lifestyle,” says Dr. Coates.

By: Paula Fitzsimmons

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