Mosquito Repellents

Sorting through boxes of my father’s family photos last month, I found a postcard I’d sent to my parents the summer I turned 14. It was mailed from Camp Zanika Lache on the south shore of Lake Wenatchee, and it read, “HELP! HELP! Please send mosquito repellent immediately! I’m being eaten ALIVE!” I discovered I had forgotten mosquito repellant my first evening at camp and frantically wrote home for help. Mosquitoes are found all over the world. They cause millions of deaths yearly from illnesses transmitted through their bite. Luckily, there are several effective mosquito repellants available.

Insect repellants work by forming a vapor. This protective vapor may be on your skin, clothing, mosquito netting, or created by sending droplets into the air as a mist. When mosquitoes come in contact with the repellent’s vapor, it keeps them from landing on you. Some repellants make you smell offensive to mosquitos, while others work by masking your smell so they cannot find you. One insect repellant works by disorienting mosquitoes so that they can't fly.

If everyone around you smells terrible to a mosquito EXCEPT you, you become a juicy target. Sitting around people wearing insect repellant without wearing any yourself is proven scientifically to increase the number of bites you'll get. I can vouch for that!

DEET is considered the gold standard for insect repellants. It was developed for the United States military in 1949 and available to consumers in 1956. Although the concentration in DEET products varies from 5% to 100%, concentrations above 50% may work longer but don't provide more protection.

Products containing 23.8% DEET have been proven completely effective in protecting against mosquito bites for 5 hours. The Food and Drug Administration (FDA) states the maximum concentration of DEET that is approved for use in children is 33%.

Many decades later, DEET is still the most common mosquito repellent. It is found in over 200 products approved by the FDA and is considered very safe if used as directed. For best results, apply it every 4-6 hours, and avoid using it on synthetic fibers, vinyl, or plastics.

Picardin is a newer insect repellant popular in Australia and Europe. Unlike DEET, it has no odor and is safe on all fabrics, vinyl, and plastic. It is not greasy or sticky and is equally effective to DEET in most situations. One application of 20% picaridin can last up to 8-10 hours. OFF! Family Care® Insect Repellent and Sawyer Fisherman's Formula® both contain picaridin.

Pyrethrins like permethrin are derived from chrysanthemums. Pyrethrins can be toxic if they contact skin for long periods. They are excellent for treating mosquito netting, boots, clothing, and sleeping bags. Permethrin is also used to treat head lice and is found in the non-prescription lice treatment Nix® crème rinse and spray. Both Coleman® Insect Treatment Gear & Clothing Spray and devices that create a mist, like OFF! Clip-On contain pyrethrins.

There is significant interest in developing effective plant-based insect repellants which are easier on the environment than DEET. The most widely used plant-based insect repellants are oil of lemon eucalyptus (OLE) and citronella oil. Repel® Plant-Based Lemon Eucalyptus pump spray contains OLE.

Other natural repellants include clove oil, lavender oil, tea tree oil, catnip oil, geraniol (from lemongrass and lemon eucalyptus), and 2-undecanone (bananas, strawberries, ginger, and other foods). 2-undecanone is also used as a dog and cat repellant.

Plant-based compounds are more pleasant to use, but their effectiveness wanes after only 20 minutes compared with 5 hours with DEET. To sustain the repellent effect of natural compounds, intense research is underway to develop sustained release delivery systems like microemulsions, microcapsules, and nano emulsions.

6 Tips on Using Mosquito Repellants Safely

1. Avoid inhaling the repellant spray.

To apply repellant to your face, spray it on your hands then rub it on, avoiding your eyes and mouth.

2. Separate sunscreen and insect repellant.

Apply sunscreen first, then repellant. Avoid using combination sunscreen and DEET insect repellant products, as sunscreen needs to be reapplied more frequently than DEET.

3. Refresh mosquito repellent at dusk.

Mosquitos are most active between dusk and dawn.

4. Use picaridin on synthetic fabrics and plastic.

DEET is safe on cotton, wool, and nylon but can damage synthetic fibers, vinyl, and plastic. 

5. Renew natural mosquito repellants frequently.

Plant-based repellants lose effectiveness after 20 minutes on your skin. Look for longer-acting formulations.

6. For children, use DEET products with 30% or less DEET.

The Zanika Lache camp website recommends packing mosquito repellant with 30% DEET.

Dr. Louise Achey, Doctor of Pharmacy, is a 43-year veteran of pharmacology and the author of Why Dogs Can’t Eat Chocolate: How Medicines Work and How YOU Can Take Them Safely. Get clear answers to your medication questions at her website and blog, TheMedicationInsider.com.

©2022 Louise Achey