Dermatologists are unanimous in stating that, like most mosquito repellents, sunscreen should be applied half an hour before sun exposure and reapplied every two hours. This interval is best suited for the skin not to be unprotected at any time.
Also, sunscreen should be reapplied whenever the person gets sweaty or gets into the water. Contrary to popular belief, water reflects only 5% of sunlight.
For this reason, we can say that sunscreen should be applied more often because water absorbs radiation from the sun.
