How to Use Insect Repellents

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A person spraying insect repellent on their arm.

Biting insects can mar an otherwise perfect day outdoors, and they have the potential to transmit serious diseases. A little knowledge about your enemy can go a long way.

This article provides some tips on safe, effective insect-repellent usage. See the companion REI Expert Advice article, Insect Repellents: How to Choose, for help on which type of repellent (e.g., DEET, picaridin, plant-based oils) is best for you.


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How Insect Repellents Work

First, a few words about your enemy.

Mosquitoes are attracted by carbon dioxide (exhaled breath), lactic acid, ammonia, phenols, humidity and other human emissions.

Repellents do not actually repel mosquitoes. They create a vapor barrier atop skin and mask or scramble the signals of attraction that humans emit. They make it tougher for mosquitoes to locate their target. Because they act as vapor barriers, repellents are rarely effective when applied underneath clothing.

Why are some people more attractive to mosquitoes? Researchers at the University of Florida speculate that human skin produces 300 or so chemicals, and one individual’s mix may be more attractive to mosquitoes than other person’s.

This means you may find one insect repellent very effective, and a friend may have great results with a different repellent.


Tips on Using DEET Repellents

  • Read and follow all directions and precautions on product label.
  • Do not apply over cuts, wounds, or irritated skin.
  • Do not apply to hands or near eyes and mouth of young children.
  • Do not allow young children to apply this product.
  • Use just enough repellent to cover exposed skin and/or clothing.
  • Do not use under clothing.
  • After returning indoors, wash treated skin with soap and water.
  • Wash treated clothing before wearing it again.
  • Use may cause skin reactions in rare cases.
  • When using sprays or aerosols, do not spray in enclosed areas; to apply to face, spray on hands first and then rub on face. Do not spray directly onto face.


Other Repellent Tips

  • Camp or take breaks in breezy areas. Mosquitoes have trouble tracking targets in windy conditions.
  • For use with sunscreen, apply sunscreen 15 minutes before sun exposure begins. Apply repellent any time after the 15-minute skin-bonding stage for sunscreen.
  • To minimize your attractiveness to insects, avoid dressing yourself or children in dark colors or wearing fragrances.
  • When using sprays or aerosols, avoid inhaling spray or mist.
  • Avoid under- and over-application.
  • Always follow label instructions on repellent labels.


Facts about Mosquitoes

  • More than 3,000 species of mosquitoes exist, and not all are blood feeders.
  • Most mosquitoes feed at dusk or dawn.
  • An adult mosquito can live up to 5 months.
  • An adult female mosquito (only females bite humans) weighs about 1/15,000 ounce (roughly 2 milligrams).
  • An adult female consumes about 5 millionths of a liter of blood during a “meal.”
  • Mosquitoes beat their wings 300-600 times per second.
  • Males find females by listening to the sound of their wings. The pitch identifies which is the correct species.
  • Mosquitoes can fly 1-1.5 miles per hour.
  • A mosquito can smell carbon dioxide you exhale from 60 to 75 feet away.

Sources: EPA, University of Florida Mosquito Information Website.



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