The best tip to stop your mask fogging up is to use baby shampoo. Baby shampoo is easy to apply. Shampoo for babies are gently, so they are easy on the eyes. So that any residue after you rinse your mask is less likely to irritate your eyes as a result. You can find baby shampoos that are hypoallergenic, most tend to be biodegradable, and they are readily available and cheap to buy. Most importantly, baby shampoo works well to clear dive mask fog.