DEET, or N,N-diethyl-m-toluamide, is the major active ingredient in most commercially available insect repellents on the market. Although considered safe by the FDA and EPA, DEET has many precautions associated with it and a less than favorable history of toxicity during World War II.[1,2] DEET is also becoming less effective against mosquitos after their first exposure to the repellent. All of which are great motivators for individuals to seek options for more natural repellents.
Research shows that many species of mosquitos have adapted to be attracted to human body odor over the scents of other animals. Our bodies produce a substance called, sulcatone, which mosquitos have developed an odorant receptor to detect. It has also been speculated that odor caused by bacterial colonies on our skin, such as S. epidermidis and C. minutissimum, may contribute to insect detection and location of humans.[5-7] Cleansing the skin in areas of higher bacterial count, such as the feet and armpits, and the use of deodorants prior to outdoor activates and where mosquitos might be encountered could potentially decrease your interaction with them.
A quick internet search can produce hundreds of natural remedies for insect repellents, but not all of these are created equal. Essential oils in particular have gained popularity recently for their use as natural repellents. Why are these oils so “essential”? An essential oil is just concentrated oil extracted from a large volume of any plant material, most commonly, through steam distillation. These oils are volatile, meaning they evaporate and become aromatic. This characteristic is what gives them the ability to repel insects.
Which Essential Oils Can be Used?
Popularized by its candle form, citronella from Cymbopogon nardus, is a strong insect repellent due to the active constituent citronellal.[9-11] One study found that adding vanillin, which is extracted from the vanilla bean, to citronella oil increases the duration of its effectiveness for up to eight hours. Caution is needed while using citronella because direct use of the undiluted essential oil can cause a skin irritation.
This plant’s oil has many volatile components, but the constituent found to have the best repellent activity is para-methane-3,8,-diol (PMD).[9,12] PMD has been shown to have DEET-like efficacy and has been endorsed by the CDC as providing “reasonably long-lasting protection” from disease carrying mosquitos.[11,12] As with all citrus family oils, lemon eucalyptus contains limonine, which causes a photo-dermatitis reaction when used topically. Direct used of the unadulterated lemon eucalyptus oil should be avoided, especially during sun exposure.
Other popular and effective essential oils include eucalyptus, patchouli, thyme, clove and lemongrass derived essential oils.[9,10,13]
Use of Essential Oils
Due to the very potent nature of essential oils it is important to remember that concentrations of 100% are avoided for skin application. Use of a carrier oil such as coconut, almond, grapeseed, soybean, or rose hip are a great and necessary way to dilute essential oils. Typical dilutions are no greater than 3% concentration (20 drops of essential oil in 1 ounce or 30 mL of carrier). It is smart to test a small area of skin to see if the dilution will cause an unwanted reaction. If there are questions about safety and toxicity an expert should be consulted.
Other options include:
- Making a spray with an oil by adding a few drops to an ounce of water, mix well by shaking and diffuse using a spray bottle
- Crafting candles with the oils
- Use an essential oil diffuser to permeate the air