Bathroom ventilation fans exhaust steamy air out of the bathroom, ultimately reducing the risk of harmful mold and mildew buildup. If you have a fan in your bathroom you should use it every time you take a shower or bath.
This urban legend says that if you take a small amount of shaving cream and rub it all over your mirror it will prevent it from steaming up. I tried this method several times and with different types of shaving cream.
Another method that supposedly stops steam on your mirrors is using a bar of soap. You rub it on the glass and buff it off just like the shaving cream. This method didn’t work for me either.
Stoner Invisible Glass Anti-Fog interior windshield treatment is actually designed for auto windows but it works like a dream for your bathroom mirror.
If you touch and smear the mirror before it dries, simply reapply. The results can last up to a month. Avoid contact with painted metal, plastic or clear coated surfaces.
How to apply Anti-Fog treatment to bathroom mirrors