Does Listerine Actually Kill Roaches? The Surprising Truth

A natural and easy-to-clean-up effective roach killer that is non-toxic and easy to reach might sound far-fetched, but most of us have that very thing in our bathrooms. This is especially convenient because outside of the kitchen, the bathroom is the next most likely place to find a cockroach infestation.

Roaches in the bathroom are annoying and sometimes downright scary, so having access to an effective cockroach repellent right there can be crucial. 

From hair spray to mouthwash to toilet cleaner, there are plenty of solutions that can help turn a roach infestation into a pile of dead cockroaches readily accessible in your home. With a pungent smell and the correct oil for roaches to be poisoned by Listerine is at the forefront of remedies for roaches. This article talks about Listerine as a roach repellent and natural pest control method. 

Will Listerine Kill a Roach?

In the realm of antiseptic mouthwash, Listerine has the highest concentration of oil for roaches to be killed by as well as other natural roach repellents that eliminate roach eggs and baby roaches too. Listerine in a spray bottle can get rid of roaches by killing them on direct contact and operating as an effective roach repellent.

This method will stop an active cockroach infestation, and more than a spray bottle of a mouthwash solution will be needed for that. 

Equally as important as getting rid of cockroaches, Listerine kills the bacteria that roaches bring into the homes that can make us ill. Using a damp cloth to wipe surfaces that cockroaches crawled on and strong mouthwash was sprayed to kill all germs and remove any residue. The smell of mouthwash should still help keep the cockroach clan at bay for a few hours. 

The chemical formula in Listerine is astringent enough to burn and suffocate roaches that it is poured on.  Adding dish soap helps Listerine stick to roaches and surfaces longer, which makes it a much more effective roach killer. This is also a good way to get it into cockroach nests that are hard to reach. The solution with soap will stick to the gaps roaches crawl out of and possibly kill or impair them as they enter our homes. 

It is becoming increasingly hard to find mouthwash brands that still use alcohol, but even alcohol-free Listerine will still burn and kill roaches or at least immobilize them, making them much easier to squish. The other oils that kill bacteria in our mouths and leave our breath smelling fresh are also common cockroach pesticide oils and do more to kill them than alcohol anyway.

An application of Listerine will kill a single roach but will not stop an infestation or offer any form of residual control after the smell is gone. Forerdaitcation of large infestations, you will want to use specially formulated pesticides or call in a professional pest control service. Mouthwash can only kill when directly sprayed or poured onto roaches and will not kill through the air or minor contact like some systematic pesticides. 

How Does Listerine Stop Cockroaches?

Despite common belief, the alcohol or “spicy” taste of mouthwash isn’t what kills the roaches. While alcohol can lead to dehydration and extreme cases of suffocation for roaches, the oils and plant derivatives in Listerine are far more potent. The most effective mouthwash variety will have a high concentration of menthol, eucalyptol, thymol, and methyl salicylate, all of which are toxic to insects like cockroaches. 

Eucalyptol is found in tea tree oil and is toxic to most bugs at high doses while also exhibiting bacterial properties. Thymol is a phenolic antiseptic that goes far in killing and sterilizing the roaches preventing the spread of harmful diseases as they scurry to die. Additionally, Methyl Salicylate, which is a natural insecticide component produced by wintergreen trees, is common in most mouthwashes. 

If included in the solution, mint oil penetrates cell membranes in invertebrates and can systematically kill American cockroaches and German cockroaches in a short amount of time. If you plan on adding peppermint oil or other insecticidal essential oils to a solution, then Listerine works better when made into a solution with other roach-killing ingredients and is a better liquid base than water for natural insecticides.

Bathroom Staples That Stop Roaches

As much as we associate cockroaches with kitchen pantries, the most common place I encounter them is in the bathroom. Knowing what I can grab to spray or pour on roaches that will kill them right away without me leaving and possibly losing track of the pest is very helpful. Since it’s not unusual to grab whatever is closest and use it to kill these invaders, let’s look at what bathroom products will actually help you. 

Product	How To Use	Effectiveness
Isopropyl Alcohol	Place on cloth and toss over roach or pour/spray directly on a cockroach to block breathing orifices	Can take a long time to kill a roach, but better than doing nothing and letting bacteria spread
Hydrogen Peroxide	Drop Roach into a highly concentrated solution or spray peroxide directly on it	Can kill roaches and sterilizes the surfaces roaches have crawled on
Listerine	Mix into solution or pour directly onto the roaches	Will kill most roaches in a few seconds to minutes, depending on the solution strength
Toothpaste	Borax will kill roaches if ingested	Better as repellent because of the minty scents and that it can be stuck in cracks and gaps
Bleach	Drop Roaches into a container or bleach or spray directly onto a cockroach where safe (tiles/counters)	Will drown a roach very quickly, and a direct spray will kill roaches with very little residual stickiness
Soap	Add to other roach-killing chemical solutions to increase tackiness	Effective at helping toxic chemicals stick to roaches and the surfaces they are on
Lysol	Spray directly at a cockroach	Will stun and kill most approaches if a direct blast to the face is accomplished
Hairspray	Spray directly on the cockroach	Will stun and kill most approaches if a direct blast to the face is accomplished

Insecticide

Most liquids added into a solution will continue to the insecticidal properties of your bug killer. Aerosols are also used best to try and kill a roach actively in your bathroom as opposed to stopping them from entering. Mixing bleach with other solutions is not recommended unless you know what you are doing, but the other bathroom liquids can be mixed to make a killer insecticide.

Alcohol and peroxide have limited use in killing but do well in cleaning the bathroom after other sprays are used. 

Repellent

Bathroom products with a minty scent are the best to repel roaches. Toothpaste used to block cracks and gaps that roaches come through can prevent access and kill roaches that try to eat through. Mouthwash as a surface spray to clean and repel can also be useful in a bathroom. Liquid soap will usually need to be combined with oils or other solutions to be effective but can help make a stick consistency that lasts longer as a roach repellent. 

Do Mouthwash and Listerine Kill or Repel Roaches?

If you want to avoid using toxic pesticides because children and pets are in the area, natural insecticides like mouthwash can use. While nothing quite substitutes for a proper pest control system, an occasional roach entering on a rainy day is not a reason to call an exterminator. Not when there are easier and better solutions available right in your bathroom. 

Mint and peppermint are scents roaches and pests do not like, so any mouthwash containing these will have some impact on roaches. The dilution of these scents and the concentration of other insecticidal ingredients in mouthwash determines how effective it is.

Listerine has a stronger repelling effect than other generic mouthwashes, and its pungent odor will work longer. The oils and chemicals also make it practical to pour into drains or on stagnant plumbing leaks for temporary treatments. Listerine does kill roaches if it hits them directly and covers them completely in your bathroom.