Avoiding Sand Fleas (aka no see ums), Mosquitoes and Other Bothersome and Disease Carrying Insects

by Doc Vikingo

Updated December 2009

Here's an updated edited version of my "Ask RSD" article on the topic in Rodale's Scuba Diving.

Sand fleas and mosquitoes can be a real bother, not to mention that they are sources of some serious tropical diseases such as leishmaniasis and malaria, respectively.

The danger and bother of insects can be substantially reduced by these precautions:

(1) Wear long sleeves and pants, avoiding dark or bright colors, especially at dawn and dusk. Protective clothing such as the "Buzz Off" brand can be useful . As an extra precaution, you may treat clothing with permethrin, as in the easy to use Sawyer Products;  

(2) Try to stay indoors at dawn and dusk when many flying insects are most active (although the mosquito that transmits dengue is most active during the daytime), and avoid sandy areas as much as possible at any time of day, especially when there is no breeze. When making reservations, make sure the resort has screened windows;

(3) Wear insect repellent. The best protection against these and other insects arguably is full strength DEET. Some divers like things such as Avon's Skin-So-Soft and Cactus Juice, less toxic products than DEET, by the science is solidly behind DEET for long-lasting effectiveness.

Most DEET containing repellents are the 15-30% range of concentration. The testing of various strengths of DEET has shown that after about 30% little additional effectiveness is to be had by upping the strength, and even less after about 50%. As such, there is simply no point in exposing oneself to more potent brews. UltraThon at 32% appears to be a good product. Used as directed over relatively brief periods of time, say a week, DEET has been shown to pose no significant risk when applied to exposed skin. If you wear lightweight, loose fitting clothes, it generally is safe to use DEET underneath. Doing so with heavy, snug fitting clothes can result in dermatological problems and worse. Be aware that DEET can dissolve synthetics like plastics, rayon and nylon, so it's best to wear natural fibers and keep it off your gear.
Relatively recently, picaridin-based repellants have been found to be quite effective and much less irritating to the skin and malodorous than DEET. The line of Cutter's Advanced products is an example.  

However, based on the published scientific research some of these products contain questionably small amounts of picaridin, e.g., Cutter Advanced Picaridin Repel at 7%, Cutter Advanced Wipes at 5.75%. It is therefore recommended that a product like Cutter Advanced Aerosol with 15% picaridin be used. Some repellants available in foreign venues contain even higher concentrations of the chemical.

(4) Avoid scented toiletries and perfumes;

(5) Upon arrival, treat your room with a bug bomb such as Shelltox or Fish (stay outside while this is being done). Touch up with spray after that as needed.


This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual and should not be construed as such.


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