Technology

Why Your Glasses Get Foggy and How to Stop It


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.

Health Tips logo

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.

Person in a sweater holds aviator glasses with foggy lenses

MarioGuti/Getty Images

6 ways to avoid your glasses fogging up

Foggy glasses can be more than just an irritating distraction. If they occur at the wrong moment — when you get ready to walk down a flight of stairs in an entryway, for example — they can be a safety hazard. Thankfully, you can do a few things to defog your glasses quickly or even prevent them from fogging up in the first place.

  • Get a fog-resistant coating on your lenses: Most eyeglass manufacturers offer the option to add coatings to your lenses that reduce fog and water buildup. If eyeglass fogging is a common problem for you, make sure your next pair have this feature. 
  • Treat your lenses with anti-fog products: There are numerous anti-fog sprays and wipes on the market, and regular application can help keep your glasses from fogging up. 
  • Use the soap-and-water trick: This is a simple alternative to buying anti-fog products. Simply wash your lenses with soap and water, then shake off the excess liquid and let the lenses dry with a thin film of soap on them. This won’t impede your vision, but it will keep fog from forming. Be sure to check with your eyeglass manufacturer to ensure the soap won’t damage any lens coatings you have.
  • Make sure your glasses aren’t too tight when wearing a mask: If you do have a mask on, you don’t want your hot breath to get trapped behind your lenses. Pushing your glasses a little further down your nose and slightly over your mask can create more space and allow cool air to flow all around your glasses, preventing fog from forming, per Warby Parker.
  • Seal your mask tightly around your nose: The best thing you can do while wearing a mask is to prevent your breath from hitting your glasses at all. Use the built-in flexible wire on your mask or some tape to create a snug seal around your nose and prevent air from escaping from the top of your mask.
  • Keep a lens cloth with you: Sometimes, you can’t avoid your glasses fogging up, so it’s always good to have a lens cloth handy to wipe them in a punch. Make sure it’s a clean microfiber cloth that won’t scratch your lenses.

Spraying a product on a pair of glasses.

Thais Almeida/Getty Images

What not to do when your glasses fog up

As with any other everyday nuisance, people are quick to come up with their own solutions to their glasses fogging up. However, some of these tactics can actually make the problem worse or even damage your lenses. Avoid using any of the following remedies for preventing foggy glasses:

  • Toothpaste: Many toothpastes contain baking soda or other abrasive ingredients that can scratch your lenses.
  • Polyethylene terephthalate film: These anti-fog films have been used in some workplace settings, but studies have shown they can actually increase moisture and droplet formation.
  • Hand sanitizer: Although some studies have shown that hand sanitizers can prevent fogging on goggles, the alcohol in these products can damage the protective coatings on many eyeglasses. 

Don’t let foggy glasses cloud your vision

Foggy glasses can stop you in your tracks or put you in harm’s way. If you typically use eyewear, it’s important to know how to prevent foggy lenses or quickly fix the problem when it occurs. With a few anti-fog products, a good microfiber cloth and proper techniques for wearing a mask with glasses, you’ll keep fog at bay and ensure you always have a clear view.