Foggy spectacles every time you step indoors? Opticians explain which cleaning trick to avoid

Outside, it's barely above freezing. Inside, the heating is on, and the moment you step through the door, your glasses turn completely white. For a few frustrating seconds, you can barely see where you're going.

It's a familiar winter problem, and there's an old household trick that promises to help: rubbing a tiny amount of dish soap (washing-up liquid) onto your lenses. The idea is to stop moisture from forming that cloudy layer.

The trick has been passed down for generations, but there's a catch. Although it can help prevent fogging, opticians disagree about whether dish soap is safe for the protective coating on modern glasses.

Why glasses fog up when you step indoors

When you come inside from the cold, your glasses are still chilly. Warm, humid indoor air touches the lenses, and some of that moisture condenses into tiny water droplets.

Those droplets scatter light, creating the familiar white haze that makes it difficult to see.

The same thing happens when you lean over a steaming pot, open a hot oven, or breathe into a scarf wrapped around your face.

Dish soap contains substances called surfactants. These reduce the surface tension of water, encouraging moisture to spread into a thin, more transparent layer instead of forming countless individual droplets.

That's why a little soap can sometimes reduce fogging. But whether it's a good idea for your particular lenses is another question.

Some opticians actually recommend dish soap

Online optician Mister Spex recommends using a little dish soap when cleaning glasses.

Its instructions suggest rinsing the lenses under lukewarm running water, gently rubbing a small amount of dish soap over them with your fingertips, and rinsing again before cleaning them with a microfiber cloth.

Dutch optician Iris Brillen also acknowledges that some professionals consider mild dish soap suitable for cleaning lenses.

However, it advises choosing a gentle formula without ingredients such as citrus extracts or moisturizing additives.

There's an important distinction here: washing your glasses with soap and rinsing it away isn't the same as leaving a soap film on the lenses to prevent fogging. The cleaning recommendations don't automatically mean that an unrinsed coating of soap is safe.

Other opticians warn about the coating

Not everyone agrees. Optical chain Pearle specifically advises against using dish soap, warning that certain formulations may contain ingredients that damage lens coatings. These coatings are often added to reduce reflections, resist scratches, and make the lenses easier to clean. Pearle recommends neutral hand soap instead and warns against household glass cleaners, vinegar, and other aggressive cleaning products.

Lens manufacturer ZEISS, meanwhile, recommends a pH-neutral dishwashing detergent diluted in water for cleaning its lenses.

The disagreement highlights an important detail: not all dish soaps contain the same ingredients, and not all lens coatings have identical care requirements.

The cleaning routine experts largely agree on

Fortunately, there's much more agreement about everyday lens care than there is about the soap trick.

Start by rinsing your glasses under lukewarm running water. This removes tiny particles of dust and grit that could otherwise scratch the surface.

Use a small amount of a mild cleaner approved for your lenses, and gently clean both sides with your fingertips.

Rinse thoroughly, then shake off excess water and carefully dry the lenses with a clean microfiber cloth.

Avoid using paper towels, tissues, clothing, or ordinary towels. They can trap abrasive particles or leave fine scratches behind.

Hot water is another thing to avoid, as excessive heat can damage certain lens coatings. The same applies to leaving your glasses on a radiator or inside a hot car.

What should you use to prevent fogging?

If your glasses mist up regularly, particularly during winter, consider an anti-fog spray specifically designed for eyeglasses.

Check that the product is compatible with your lens coating, and follow its instructions. Some sprays need to be applied to clean, dry lenses and left in place rather than rinsed off.

And if you're tempted to try the traditional dish soap trick, ask your optician first, particularly if your glasses have expensive coatings or are still under warranty.

The old trick may help with the fog, but protecting your lenses is just as important as keeping them clear.