A: DEET (diethyltoluamide) is the active ingredient in many quality insect repellents, eg Repel, Rid, etc, and is very important to help avoid mosquito bites, and other insects, in the tropics. This is good protection against dengue fever, and a DEET containing repellent should be used, with sensible clothing and other anti-mosquito measures. Repellent should be used on exposed skin with 4 hourly applications when outside exposure occurs during the day or evening, and should washed off children before bed, ideally with children sleeping under a mosquito net or in an air-conditioned room.
Products of a 30%-50% concentration of DEET are optimal for adults, and higher concentrations do not add much more efficiency. In small children under 6 years however, we prefer that a 10% product is used, as this avoids any potential issues of adsorption and toxicity. (In fact one would need to drink it to cause any problem, that's why it must be stored out of reach of children). So for a 2 week holiday, use of 10 % DEET-containing repellent is strongly recommended and will cause no problems at all.
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