Is Listerine a Mosquito Repellent?

An Urban Legend or Based on Fact?


Alberto E. Rodriguez/Getty Images

Description: Viral text
Circulating Since: 2007
Status: Unsubstantiated

Summary: Viral message circulating via email and social media claims spraying an outside area with Listerine mouthwash repels and/or kills every mosquito in the vicinity.

Email contributed by J.F., October 9, 2007:

Subject: mosquito killer
The best way of getting rid of mosquitoes is Listerine, the original medicinal type. The Dollar Store-type works, too. I was at a deck party awhile back, and the bugs were having a ball biting everyone. A man at the party sprayed the lawn and deck floor with Listerine, and the little demons disappeared. The next year I filled a 4-ounce spray bottle and used it around my seat whenever I saw mosquitoes. And voila! That worked as well. It worked at a picnic where we sprayed the area around the food table, the children's swing area, and the standing water nearby. During the summer, I don't leave home without it.....Pass it on.
I tried this on my deck and around all of my doors. It works - in fact, it killed them instantly. I bought my bottle from Target and it cost me $1.89. It really doesn't take much, and it is a big bottle, too; so it is not as expensive to use as the can of spray you buy that doesn't last 30 minutes. So, try this, please. It will last a couple of days. Don't spray directly on a wood door (like your front door), but spray around the frame. Spray around the window frames, and even inside the dog house if you have one.

Analysis: There are no scientific studies to confirm or disprove these anecdotal claims, though laboratory tests have shown that standard chemical-based mosquito repellents are generally more effective and longer-lasting than botanical-based alternatives, of which Listerine antiseptic mouthwash would have to be counted as one.

The primary active ingredient in Listerine is eucalyptol, a derivative of eucalyptus oil, which in turn is commonly used in botanical insect repellents. According to various clinical studies, it actually does repel mosquitoes. However, the eucalyptus-based compounds tested in these studies contained much higher concentrations of the essential oil than that found in Listerine Antiseptic — 40 percent to 75 percent concentrations as opposed to Listerine's .092 percent — and were applied topically, not sprayed in the air or on surrounding objects. Given Listerine's extremely low eucalyptol content, it's doubtful the product would function very effectively as a repellent — not for long, at any rate — even if applied directly to the skin.

The claim that Listerine sprayed around door and window frames actually kills mosquitoes is even more dubious. Listerine consists mostly of water and alcohol, which means it evaporates quickly whenever and wherever it is sprayed. I have no doubt that drenching mosquitoes with the stuff would kill a significant number of them, but there's little reason to suppose that spraying it on hard surfaces would have any lingering mosquito-killing effect.

Sources and Further Reading

Comparative Efficacy of Mosquito Repellents Against Mosquito Bites, New England Journal of Medicine, 4 July 2002

Field Trials on the Repellent Activity of Four Plant Products, (Abstract) Phytotherapy Research, March 2003

Insect Repellent Ratings, ConsumerSearch

Home Remedies May Work, but Do So at Your Own Risk, My Clay Sun, 26 March 2008

Eucalyptol, Wikipedia