Understand the importance of the active ingredients

When searching for bug spray, many don't understand what "active ingredient" means or what DEET really is. However, there are many different pros and cons of DEET and other active ingredients, some that may even affect your health and safety. Learning what to look for in insect repellents will help you find what products are appropriate for you and the situations you might be in while backpacking.

Understanding Active Ingredients

Traditional (DEET and Picaridin)

• Pros: Most effective and longer lasting. It has a long record of safety.
• Cons: It's chemical-based. DEET may harm fabrics or surfaces

Natural (Plant-based formulas)

• Pros: Derived principally from plants. It won't damage fabrics or surfaces.
• Cons: The duration of effectiveness varies and reapplications are usually needed.

DEET was widely regarded as the most effective repellent available. It has been used safely in the outdoors since 1957. Some formulas repel insects for up to 12 hours. Read more

Picaridin was developed in Europe, and has been available in the United States since 2005. 5% - 15% picaridin formulas are comparable in effectiveness (2 - 6 hours)to low-concentration DEET. Read more

Natural Repellents are made from plants, e.g. oil of lemon eucalyptus, citronella, and soybean/geranium oils. They offer protection for short-term use, 1 - 6 hours. Read more

Permethrin is a chemical applied to fabrics by spraying or soaking. It can last up to 70 washes, and there are no known safety issues. Read more

Q: What active ingredient stays effective the longest?

A: DEET - in high concentrations (30% or higher) or when used in a controlled-release formula (which typically uses a 30%-35% concentration).

DEET (Diethyl Toluamide) is a chemical. To some people, the thought applying it their skin makes them uneasy. Yet DEET has been in use since 1957 and has been repeatedly tested for toxicity. The Centers for Disease Control and Prevention (CDC) recommends its usage and considers it safe when applied according to label instructions.

DEET is the only active repellent ingredient available currently in high concentrations in the U.S. Why? Only DEET's higher concentrations have been screened extensively for toxicity (a lengthy and expensive process, costing millions). Such data is required by the Environmental Protection Agency, which regulates repellent ingredients in the U.S. Over time, newer repellents will likely be researched more extensively and higher concentrations will become available.

In lower concentrations, active ingredients (DEET included) provide shorter-term effectiveness. The duration of effectiveness will vary by active ingredient.

For example, in an often-cited study published in the New England Journal of Medicine in 2002, DEET at 6.7% was effective for 112 minutes before the first bite was registered. Citronella at 10% yielded a bite after 19.7 minutes. A 2004 study produced similar results.

What does that mean for you? Base your choice on the amount of time you plan to spend outside. If you are planning a vigorous all-day hike, choosing a high-concentration repellent makes sense — you will have less need to reapply the repellent. If you are planning just a short walk or a casual backyard activity, you could choose a low-concentration repellent — usually effective for 1 to 4 hours.

Q: How safe is DEET?

• Lab tests have shown that skin absorbs DEET, but is eliminated from the body through urine (the highest concentrations being expelled several hours after application).
• Human and animal studies indicate that DEET does not accumulate in the body.
• DEET-related illnesses have been reported in medical literature, but typically because DEET was used inappropriately, excessively and/or over a prolonged time.
• Some medical professionals wonder about chemical exposure and a child's brain development. One study using rats indicated DEET produced a neurological effect; several other studies showed no neurological link.
• No repellent, DEET-based or otherwise, should be applied close to the eyes or on broken skin.

 

Traditional Active Ingredients

DEET (N,N-diethyl-3-methylbenzamide, or N,N-diethyl-m-toluamide)

Pros:

• Globally regarded as the gold standard of repellents
• Developed for military use in 1946; approved for public use in 1957.
• Regarded as the longest-lasting, most effective active ingredient in the insect-repellent arsenal; some formulas provide up to 12 hours of protection.
• Used safely by humans in small or moderate amounts for 5 decades; has been the subject of numerous studies since its introduction.
• According to the American Academy of Pediatrics, suitable for children at least 2 months old in concentrations of up to 30% when used according to directions on product labels.

Cons:

• DEET is a "plasticizer." It can have adverse affects on most synthetic fabrics (such as rayon or spandex), auto paint, watch crystals, varnished surfaces, golf-club grips, leather and plastic. It will not damage cotton, wool or nylon.
• A potentially objectionable odor.
• Less effective against some flies. For problematic flies, consider repellents that use:
  • Picaridin
  • IR 3535
  • DEET combined with a fly-targeted ingredient such as R-326

Picaridin (KBR 3023)

Pros:

• Developed in Europe in 1998; approved for use in U.S. in 2005.
• Effective against mosquitoes and ticks; more effective against flies than DEET.
• Causes no damage after contact with synthetic fabrics or painted/varnished surfaces.

Cons:

• Currently available only in lower concentrations (starting at 5.75%; a 20% version will be available soon).
• Duration of effectiveness is fair to good (3 to 8 hours).

IR 3535 (3-(N-butyl-N-acetyl)-aminopropionic acid ethyl ester)

Pros:

• Used in U.S. since 1999.
• Moderately effective against mosquitoes, ticks and flies; potentially may also repel bees and wasps.
• Registered as a biopesticide with EPA.
• Exhibits lower toxicity as compared to some other active ingredients.

Cons:

• Some researchers consider its duration of effectiveness as unpredictable.
• Can damage plastics.

Natural Active Ingredients

Oil of Lemon Eucalyptus (natural oil is extracted lemon eucalyptus leaves and twigs)

Pros:

• Used in the U.S. since 2000.
• Effective against mosquitoes, ticks and some flies.
• Causes no damage after contact with synthetic fabrics or material surfaces.

Cons:

• A strong, distinctive odor.
• Label instructions advise applying it to skin no more than twice a day; may irritate some sensitive skin.
• Duration of effectiveness is fair (up to 4 hours)

Citronella (natural oil is derived from dried cultivated grasses)

Pros:

• Used in the U.S. since 1948.
• Effective against mosquitoes, ticks and some flies.

Cons:

• A potentially objectionable odor.
• May irritate some sensitive skin.
• A faint risk to stain some fabrics.
• Duration of effectiveness is low to good (1 to 6 hours).

Herb-based formulas (ingredients range from soybeans to crushed chrysanthemums)

Pros:

• Effective against mosquitoes and ticks.
• In some cases, a less objectionable odor.

Cons:

• Duration of effectiveness is unpredictable.

Active Ingredients for Fabrics

Permethrin (a chemical insecticide; applied to clothing either by soaking or spraying)

Pros:

• Used in the U.S. since 1979.
• Effective against ticks, mosquitoes, mites and up to 50 other insects.
• Application can last up to 6 washings and for 6 weeks.
• Won't stain fabrics; almost never irritates skin.
• Considered to be biodegradable; shown to not accumulate in the environment.
• In some circumstances may preclude the use of topical repellents, especially if ticks are the main concern.
• Repels insects; kills insects that contact the treated clothing and bed-netting.

Cons:

• Care is needed to avoid flushing permethrin in liquid form into a sewer system or water supply. Once dry, however, there is no risk.

 

Additional Resources

• Wild Backpacker - Insect Repellent Buying Guide
• Wild Backpacker - Insect Repellent FAQ
• REI: Expert Advice - How to Choose Insect Repellent

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