Scientific research about the effect of applying both an DEET-based insect repellent AND a sunscreen is suggesting that each product will each cancel out their effectiveness against insects and the sun.

A professor at the University of Manitoba in Canada has discovered the potentially serious effect of applying a sunscreen and insect repellent at the same time. Professor Xiaochen Gu advises that people first apply the sunscreen and then wait for at least 30 minutes before using a DEET-based insect repellent directly on the skin.