Have you heard the rumor that listerine can be used to kill roaches? In my 20 years of pest control experience, I’ve heard this rumor a few times, and I thought it was officially time to test this theory and see if it’s true or not. Welcome to our ultimate guide on does Listerine kill roaches, or is it another old wives tale?
Does Listerine Kill Cockroaches?
The answer is yes, Listerine has been known to kill a cockroach, but only if you apply it directly, full-strength on a single roach. In our testing, Listerine simply wasn’t worth it and you’re better off using a more effective pest control method than this product.
Of course, this is true of many home remedies meant to kill roaches. For instance, if you spray Windex directly on a cockroach for a couple of minutes, it is bound to eventually die, even if it manages to crawl away from you. The same is true if you apply hairspray or pure rubbing alcohol to these creatures.
So technically the answer to does listerine kill roaches is yes, but there should be some asterisks behind that statement.
That being said, Listerine just really isn’t a practical cockroach infestation solution. It works well enough to kill a single cockroach, but it just isn’t powerful enough to work on a full infestation. If you are looking for an effective house treatment for roaches, listerine just isn’t it.
What is Listerine?
Listerine is not meant to be used as a pesticide. It is an antiseptic mouthwash, patented in 1879, that is sold to treat gum disease, mouth sores, bad breath and generally is used as a product to kill bacteria. So what does it contain that has given it the reputation of a supposed bug killer?
Listerine contains alcohol, eucalyptol (from the eucalyptus plant), menthol, methyl salicylate, and thymol, which help with killing bacteria in your mouth. Here are the various effects that these substances can have on a cockroach.
How The Alcohol In Listerine Affects Cockroaches
Listerine is 26.9% alcohol solution, the equivalent of 54% proof vodka. Your cockroaches won’t get drunk, but if the alcohol is ingested, they will become so dehydrated that they eventually die.
The key word here is eventually, as cockroaches are notorious for tolerating the worst poisons and returning for more.
How The Eucalyptol In Listerine Affects Cockroaches
Eucalyptol is a potent mixture of highly aromatic toxic cooling compounds that could kill a roach if poured straight onto the bug. Unfortunately, Listerine only contains .092% Eucalyptol, which makes it a mild deterrent rather than a killer of cockroaches that your house deserves. Unless you want to pour the entire bottle on the roach…
How Does The Thymol In Listerine Kill Roaches?
Purdue University did a study on “green” pesticides and found that plant-based oils, such as the thymol in Listerine, were effective at depressing the nervous system of pests such as cockroaches and bed bugs. This paralyzes them and may eventually kill them.
Why Do Roaches Hate The Menthol in Listerine?
Menthol is a distillate of mint that, according to a study done at Auburn University, does kill roaches in 24 hours, as long as the application is full strength and topical.
However, the roaches must be doused in the essential oil to be effective. Listerine contains .042% menthol, enough to repel roaches but not kill them.
Does The Methyl Salicylate in Listerine Kill Roaches?
Methyl salicylate is also known as wintergreen oil. It is a natural extract of salicylic acid, the same acid found in aspirin. It comes from spruce, birch, and willow trees, but it can also be manufactured by synthesizing salicylic acid with methanol. Its aroma repels roaches.
A study published in Urban Etomol shows that mint oils such as wintergreen kill American and German cockroaches as long as it is applied topically. The wintergreen in Listerine is not quite strong enough at just .06% to kill roaches. According to the Urban Etomol study, it would take 2.57% mint oil to kill American cockroaches and 5.95% for German cockroaches.
2 Ways That Listerine Can Kill Roaches
A cockroach will die from having Listerine poured on it, but it requires direct contact and a significant amount of listerine, so if that’s your goal we suggest just keeping the Listerine in your bathroom.
That being said, there is some evidence in our testing that Listerine can help to repel roaches more effectively than it can kill them.
Listerine in A Spray Bottle To Repel and Kill Roaches
During our testing the stopping power of Listerine on roaches is very low, so we just resorted to using this product more as a roach repellent, since these chemicals are safe for humans and overall the scent is quite pleasant. Here are the steps we used to apply the Listerine!
Listerine And Peppermint Oil Spray
A variation on the above DIY cockroach is to give the Listerine a bit more power by adding peppermint oil. Like menthol, peppermint oil repels roaches.
To make Listerine and peppermint essential oil repellent:
- Fill the sprayer bottle 3/4 of the way with Listerine and add a quarter cup of water.
- Then add five drops of peppermint oil. If you need a strong roach killer, add a few drops more.
- Twist the nozzle on tight, and then shake it well.
- Seek out the cockroaches you wish to exterminate and drench them by shooting them with a pure stream of Listerine and peppermint oil.
This particular blend of peppermint essential oil and Listerine is quite potent, so be sure to wear protective goggles and a mask to prevent splashes to the eye and the inhalation of toxic fumes.
Killing Roaches With Listerine Tips
Although we don’t really recommend using Listerine products to directly kill cockroaches if you are going to use it as a pest control method around your house, then here are some tips.
Aim Your Spray Bottle At The Cockroaches
If you are using a spray bottle to kill a cockroach, make sure that you turn the nozzle so that you are using a hard spray and not the wide spray, which will be too dispersed in strength to kill them.
Make sure you direct the spray right at the bug to fill all the spiracles in its hard shell with the liquid.
If the cockroach starts skittling away, go after it, and don’t stop squirting it with Listerine. The force of the liquid hitting the roach can also help weaken and kill them. Be relentless!
Suffocate Them With Mouthwash
Cockroaches are not necessarily killed just by the toxic ingredients in mouthwash. Whether drenching with liquid Listerine or using a Listerine and peppermint oil spray, keep in mind that the wetter the bug is, the more likely it is to slow down and die of suffocation.
Use Listerine Bug Spray With Caution
The substances in Listerine, such as alcohol, thymol, and wintergreen oil, can overwhelm the nasal receptors of humans and make them feel dizzy, weak, or shaky.
To escape the strong, pungent smell of Listerine bug spray, be sure to open a window and wear a mask before spraying.
Clean Up Dead Cockroaches Right Away
Unfortunately, an effective cockroach repellent might draw more cockroaches into your home.
According to a Perdue extension article about cockroaches, dead specimens emit pheromones that alert other cockroaches of their death. These pheromones are essentially a dinner bell that invites them to come feast on their friend’s body.
To avoid attracting additional bugs, dispose of any dead cockroaches as far away from their nesting place as possible.
Other Household Roach Remedies:
- Can Ammonia Kill Cockroaches
- Can Borax Kill Cockroaches
- Can Lemon Juice Kill Cockroaches
- Can Lysol Kill Cockroaches
- Can Vinegar Kill Cockroaches
- Can Bay Leaves Kill Cockroaches
- Can Salt Kill Cockroaches
FAQ
Here are frequently asked questions about DYI Listerine bug spray.
Where would I spray Listerine bug killer?
The best approach is to spray it right into cockroach nests. Certain areas in your home may be more prone to cockroach infestation than others.
Kitchen sink drains and bathroom drains are popular hideouts for cockroaches. They lurk where there might be cold condensed water, such as beneath a fridge or in the laundry room.
Cockroaches hide in the bathroom vanity or kitchen cupboards. Cockroaches eat almost anything, so keep all of your cupboard shelves free of food and cosmetic residues.
Is Listerine Bug Spray Safe For Children and Pets?
Keep children and pets away from your sprayed area for at least an hour after spraying Listerine on roaches.
Listerine fumes are toxic because of their high thymol, alcohol, and eucalyptus content. These toxic substances can irritate airways, skin, and eyes.
It is advisable to keep cats and dogs away from essential oils of all kinds, including wintergreen, thymol, and menthol, all ingredients in Listerine.
Final Thoughts On Listerine and Cockroaches
Homemade Listerine bug spray may not be as effective as a pesticide for killing roaches, and in most cases, it may simply repel them before they learn to tolerate the odor and toxic effects.
Listerine is also more effective when you use it with peppermint oil, but it is not likely to get rid of a roach infestation.
Still, it is a mostly tolerable, temporary solution for dealing with individual bugs, and it may succeed in keeping a roach infestation at bay for a limited amount of time.
If you are infested with roaches or other insects, I suggest you use a traditional insecticide, trap, or bait to eliminate your infestation!
Resources:
https://extension.entm.purdue.edu/publications/E-23/E-23.html