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The amount of active ingredient by volume or weight does not indicate the toxicity of the product, but its duration: a product with 80 % DEET is not more effective than one with 10 % DEET, provided it is applied with sufficient frequency (perhaps every two hours, versus the 14 hours of a product with 80 % DEET). It is very unlikely that require 10 hours of continuous protection in circumstances that prevent the application of the repellent later. In fact, it may be more beneficial to use a product with lower concentrations of active ingredient, such as Nopikex to 22 %, or by 23.8 %, that would require your application after approximately eight hours of exposure, a product with 80 % DEET or even 100 %, which can provide protection for up to 10 hours. The main reason is psychological, as it is better to be fully aware of the constant threat of vector-borne diseases in endemic areas (something that is achieved by applying a mosquito repellent every few hours) to use a product that offers protection throughout the day, which could cause a person to overlook the need of reaplicarlo after such a long period. Regardless of the percentage of active ingredient by volume/weight or age of the person using the repellent, any repellent topical application must:

Never use in areas of the skin which will then be covered, for example, do not place it in the arms and then wear a long sleeve shirt.
Never apply on the lips, areas eye (near the eyes), inside the nostrils, or around the genital areas of the body.
Should be washed completely within a period of 24 hours and then re-apply if necessary.
Must be applied with care in the hands of the children, since they probably will tend to rub your eyes or take your fingers to the mouth without being fully aware of the active ingredient in insect repellent; although it is probable that none of these actions may cause serious harm, surely they will cause a discomfort considerable.