Why Do Glasses Fog Up in Winter?

Cold lenses plus warm air equals condensation. Water vapor in the air transforms into liquid form when the temperature changes and that liquid clings to a surface—in this case, your lenses. When the fog clears from your lenses, the opposite happens—the liquid evaporates, turning back into a gas. Taking your glasses off and holding them in front of a blowing vent or waving them around gently can speed up this process, but wouldn’t it be nice to avoid the foggy lenses altogether?

How to Keep Glasses from Fogging Up:

Pick fog-free materials

Anti-reflective treatments not only reduce glare, they often include a hydrophobic coating that resists water, smudges and fogging.

Most sports sunglasses and ski or snowboard goggles are designed to allow venting and prevent fogging, even when you’re breaking a sweat. Anti-fog technology is common in sports lenses and can make eyewear safer by preventing vision-obscuring fog on the lenses. Prescription glasses that rest further from the face will also allow air to circulate around the lenses to minimize fogging.

Clean your glasses

Dirt, smudges, and scratches give condensation more to cling to. Keep your lenses clean, avoid leaving fingerprints on your lenses, and handle glasses gently to prevent scratches. Cleaning your lenses regularly can help reduce fogging. A simple way to clean your glasses - is to use a gentle dish soap—a one-two punch as dish soap’s properties can reduce fogging.

Because the surfactants in dish soap reduce surface tension, a thin film of water coats the lens instead of a mist. Though there’s still moisture on the lens, it allows light to pass through rather than it being scattered in multiple directions as it is through droplets—so your vision isn’t obscured by fog.

A lens cleaner or reusable or single-use anti-fog wipe made specifically for preventing foggy lenses is safest for your lenses. Similar to dish soap, surfactants are part of how an anti-fog treatment works. Other treatments not made for glasses can harm anti-glare or photochromic coatings, and can void any warranties your lenses carry.

Get your frames adjusted

If your glasses keep fogging up, letting more air flow around the lenses can reduce the problem. Adjusting the nose pads or arms slightly can help keep your glasses where they belong. Frames that sit too close to your face may need adjustment by your optometrist, but there’s only so much they can do. If fogging is a common occurrence, you may be off—consider a new frame with more space between the lenses and your face.

If all else fails, try this glasses hack

The best fix is one that’s actually made for glasses, but if you’ve tried everything else and are still searching for a solution, a tiny dab of shaving cream can reduce fogging. Spread it over both sides of the lenses and let it dry, then gently rub the shaving cream off with a microfiber cloth. The film the shaving cream leaves behind reduces surface tension, so the moisture slicks away. If you must use this technique, avoid shaving foams that include lotions as they’ll damage your lenses.

Baby shampoo or gentle dish detergent mixed with water offers a similar fix. It can be mixed in a small spritz bottle and used as necessary. Any topical solution must be re-applied often as it wears off.