Here's something I pulled from another board:
"Sand fleas & mosquitoes can be a real bother, not to mention that they are sources of some serious tropical diseases.
The danger & 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
http://www.permethrin-repellent.com ); (2) Try to stay indoors at dawn and dusk when many flying insects are most active, 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 is full strength DEET. Some divers like things such as Avon's Skin-So-Soft & Cactus Juice, less toxic products than DEET, by the science is solidly behind DEET for 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 virtually none after about 50%. As such, there is simply no point in exposing oneself to more potent brews. UltraThon at 32%
http://www.3m.com/us/home_leisure/s...ultrathon.jhtml 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 & worse. Be aware that DEET can dissolve synthetics like plastics, rayon & nylon, so it's best to wear natural fibers & keep it off of your gear; (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."