Letter Re: West Nile Virus

Hi Hugh,

I recently heard from two people (one who stayed in Florida, the other in Texas) that restaurants were hanging zip-loc bags with water in them around their outside dining areas. Apparently, that repels mosquitoes and flies. Although no one could provide an explanation as to why it worked, I have a theory that may explain it. When sunlight passes through water droplets in the air (when it’s raining) the light bends as it passes through the surface of the water droplet. The different wavelengths of light bend at different angles. A second bending occurs when the light exits the droplet on the other side. This causes the rainbow that we see when it is raining somewhere and the sun is also shining. (You can replicate this on a sunny day by spraying a fine mist out of your garden hose.) Even though insects may not be the most intelligent species on the planet, it’s quite likely they also see the rainbows and associate them with dangerous projectiles (rain) and take cover. Insects likely have eyes that are more sensitive to light than ours and can detect rainbows emanating from the bags of water. They think it’s raining and therefore avoid the area. This is definitely worth a try and may aid in keeping mosquitoes at bay. – P.B. in Maine

Hugh Responds: I have not heard anything about that method of mosquito repellent, but I am highly skeptical. Around 1900, it was already known that “germs” were spread through common points of contact, such as telephone handsets. Several companies marketed “Hygienic Telephone Discs”, which were simply disposable paper discs that one placed over the mouthpiece of the phone to protect the user from picking up germs or spreading germs to the phone handset. To be especially effective, you could soak the paper in an antiseptic as well. However, the uneducated person did not understand how the paper disc protected the user from the germs, so it became quite common to find these paper discs hanging on the telephone lines outside of homes. The owners reasoned that if the discs protected you from picking up germs from the phone, why even bother letting the germs inside the home through the telephone lines in the first place? I suspect, in a similar vein, the sealed bags of water are related to the instructions of not leaving open stagnant bodies of water around for mosquitoes to breed in rather than any repellent ability that they may have.

In the meantime, my wife suggests the following recipe for making 8 oz of mosquito repellent from essential oils:

  • 2 oz. of rose geranium essential oil,
  • 12 drops of peppermint essential oil,
  • 8 drops of lavender essential oil,
  • 6 drops of clove essential oil,
  • 2 drops of sage leaf essential oil,
  • 2 drops of eucalyptus essential oil, plus
  • Enough base oil to bring the volume to 8 oz. The base oil can be olive oil, almond oil, coconut oil, or (for an especially light option) sesame oil.

My wife prefers the heavier oils as she has dry skin and the lighter oils are quickly absorbed. I prefer the lighter sesame base oil. An application seems to last about two to three hours, depending on how quickly your skin absorbs the oils. We place the repellent in an 8 oz spray bottle and shake before each use. Spray it on exposed skin and then rub it in so that it has an even application. So far, it seems to be as effective as the DEET products, though the application doesn’t last as long. The aroma is not too feminine or masculine and is rather pleasant, so even children don’t fight it. We also use it on our dog, though only on areas of her body where she can’t lick (on her collar or back of neck) and it deters not only mosquitos but other pests as well, such as fleas and ticks. You can mix just peppermint and lavender oils in coconut oil for use on dog’s paws, between toes and on torso, as it is safe for their ingestion and will aid in warding off fleas, ticks, and other bugs in those areas of their body also.