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Listerine
Although Listerine is a household name as a mouthwash, it was originally developed as a surgical antiseptic. Joseph Lister developed Listerine for the operating room in 1879. It did not become an over the counter oral care item until 1914.
152 Questions
Does Listerine work as a mosquito repellent?
Unfortunately 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 (and Listerine Antiseptic mouthwash would have to be counted among the latter). The primary active ingredient in Listerine is eucalyptol, a derivative of eucalyptus oil, which in turn is commonly used in botanical 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% to 75% concentrations as opposed to Listerine's .092% -- and were applied topically, not simply 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 killed mosquitoes is even more dubious. Listerine consists mostly of water and alcohol, which means it would evaporate 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 is little reason to suppose that spraying it on hard surfaces would have any lingering effect.
