Eyeglasses have a straightforward task: to help you see better. When fog gets in the way, they do the exact opposite. For the more than 166 million Americans who wear prescription eyewear, foggy glasses are a common nuisance — sometimes even a dangerous problem. Here’s why it happens and what you can do to keep your glasses from fogging up.
Why do glasses fog up?
Foggy glasses are the result of condensation, the simple chemical process that occurs when water vapor cools down enough to turn from a gas back into its liquid state. This can happen quite suddenly when there is a drastic difference between the temperature of a surface and the surrounding humid air.
If your lenses are cool and you step into a warm area, condensation will occur when the warm air touches your glasses, as Cleveland Clinic reported. So, if you’ve been outside on a cold winter day and walk into a heated room, your glasses might fog up immediately. The same thing can happen when you step out of the air conditioning into hot, humid summer air.
For many, the problem of glasses fogging up became especially common during the COVID-19 pandemic. Masks direct your warm, moist breath upward onto your glasses, and when those glasses are cool, you’re likely to see fog.