Rocha et al.,
I'd be cautious about using DEET at 100%. DEET may be the best (or only) repellent that really works, but there are indications that high concentrations and/or long-term use can pose health risks, though there is no hard proof. (Living in Bali, this is subject that I'm very concerned about - I have used products containing DEET almost every evening. for the past 3-4 years!)
A well-known study published in the New England Journal of Medicine in 2002 concluded that while alternative formulations can repell mosquitos for a short periods, only products containing DEET offered real protection for significant periods. The highest concentration DEET product tested, OFF Deep Woods, at 23.8%, repelled mosquitos for up to 360 minutes. Lower concentrations of DEET also worked, but for shorter periods of time.
http://content.nejm.org/cgi/content/full/347/1/13 {abstract}
http://content.nejm.org/cgi/reprint/347/1/13.pdf {full article}
http://content.nejm.org/content/vol347/iss...large/04t1.jpeg {results table}
http://content.nejm.org/cgi/content/full/347/21/1719 {discussion in later nejm issue}
The West Nile virus crisis has led to some new studies and greater attention to alternatives, but nothing has emerged that is obviously as effective as DEET products. My current take on the status of mosquito repellents is as follows:
1. DEET containing products work, but one should minimize use (i.e., sleep in a mosquito net) and avoid products with concentrations of DEET greater than 30%. (Some physicians say concentrations higher than 30% may be justifiable for people working in areas with intense black fly or high risk of exposure to ticks carrying lyme disease, etc.)
2. Avoid applying products containing DEET at the same time or shortly after applying sun-screen. (In dengue-fever areas, including most of Indonesia, people are quite correct to apply repellent in the middle of the day.) Some ingredients in sunblock can hugely increase the amount of DEET absorbed.
3. Alternatives to DEET that some authorities (CDC) say may have comparable effectiveness include:
- Picaridin (AKA 3023, Icaridin). One product has been approved in the US, more in Oz and Europe. I've tried one, didn't like it.
- Oil of lemon eucalyptus (P-methane-3,8-diol, or PMD). I'm interested in trying this, but nobody claims that the effectiveness is better than low-concentration (very low) DEET products.
Unfortunately, claims for oils of garlic, fennel, etc. don't seem to hold up. Citronella oil compounds apparently reduces the number of bites, but don't prevent them.
Other sources of information:
http://www.cdc.gov/ncidod/dvbid/westnile/r...s/uprepinfo.pdf
http://www.cdc.gov/ncidod/dvbid/westnile/q...t_repellent.htm
http://www.epa.gov/pesticides/health/mosquitoes/insectrp.htm
Frogfish (Robert Delfs)
