There’s nothing more annoying than your windows fogging up right as you’re about to drive off. Cold winter morning or humid summer afternoon, the visibility drops in seconds, and that’s not just irritating. It’s genuinely dangerous.
The auto store has a whole shelf of anti-fog products. Meanwhile the internet is full of DIY hacks that promise the same result using stuff already in your bathroom cabinet.
So which actually works?
First, Why Your Windows Fog Up
A quick bit of the “why,” because it explains why some hacks work and others don’t. Your windows fog when warm, humid air meets cooler glass, and the moisture condenses into tiny droplets. In winter, that’s your warm breath and body heat hitting a freezing windshield.
So the job of any anti-fog treatment is simple. Change the glass surface so moisture spreads out into a thin, invisible film instead of beading up into those opaque little droplets you can’t see through. Every method below is really just trying to do that one thing.
The DIY Hacks
1. Shaving Cream (the best DIY option)
What it is: An everyday bathroom item that doubles as a surprisingly effective anti-fog treatment for your glass.
Why it works: Shaving cream contains surfactants and emollients that leave behind a thin, invisible film, the same basic idea as a store-bought anti-fog product. Controlled tests, including ones by scuba divers and glasses wearers, show it performs nearly as well as commercial products for short-term fog prevention.
How to do it:
- Spread a thin layer on the inside of the glass.
- Buff it until the glass is completely clear.
- Make sure you buff it fully, or you will trade fog for streaks.
2. Baby Shampoo
What it is: The same mild soap swimmers use on their goggles, repurposed to keep your car glass clear.
Why it works: Baby shampoo contains gentle surfactants that leave a thin, transparent layer on the glass. That layer stops moisture from beading into the tiny droplets that make fog, so the water spreads out invisibly instead.
How to do it:
- Put a small dab of baby shampoo on a clean cloth.
- Smear it evenly across the inside of the glass.
- Lightly rinse or wipe, without scrubbing it all off, until the glass is clear. Get the balance wrong and you will be left with streaks or a soapy haze.
3. Raw Potato
What it is: The old-school forum favourite, a cut potato rubbed straight onto the glass.
Why it works: The starch in a raw potato leaves a thin, water-attracting film when you rub it on the glass. That film can reduce fogging for a short while, though it is far less reliable than the other methods.
How to do it:
- Cut a raw potato in half.
- Rub the cut side over the inside of the glass to leave a light starchy layer.
- Let it dry, then buff it clear. Be warned: you are about as likely to end up with a streaky, dull window as a clear one.
4. Hand Sanitizer (don’t bother)
What it is: A quick fix people reach for that, honestly, you should skip.
Why it does not work: Hand sanitizer is mostly alcohol, which evaporates almost instantly and leaves nothing behind to actually fight fog. Worse, it can damage some window tints and interior coatings, so it risks doing harm with no payoff.
How to do it: Don’t. In testing it was the worst performer by a wide margin. If this is all you have, you are better off just wiping the glass with a dry cloth.
The Store-Bought Option
A purpose-built automotive anti-fog product is the benchmark for a reason. These work by leaving a hydrophilic coating on the inside of your glass that spreads moisture into an even, invisible film. Application is easy: wipe it on with a cloth, let it haze over, then buff it off. In real-world testing, a good one stays clear through repeated foggy conditions and lasts far longer than any of the hacks.
The trade-off is simply that you have to buy it and keep it on hand. If you want the most reliable results without fuss, a trusted automotive anti-fog treatment is the one I’d keep in the glovebox. And since fog treatment only works on genuinely clean glass, pair it with a proper glass cleaner and microfiber cloths, because applying any of this over a dirty windshield just smears grime into your film.
How They Actually Performed
To make it fair, the test recreated real fog: boiling water inside a cold car cabin to trigger instant condensation across the glass. Here’s how each section held up.
- Store-bought anti-fog: crystal clear. The gold standard.
- Shaving cream: also crystal clear when buffed well. The best DIY result by far.
- Baby shampoo: worked, sort of, but left a slightly filmy look that got more noticeable with repeated fogging.
- Raw potato: added a thin fog-resistant layer but dulled the glass and wasn’t reliable.
- Hand sanitizer: immediate fog. Total failure.
The Verdict
Here’s the honest mechanic’s take. If you’re caught in a pinch, shaving cream is a genuinely effective stand-in, just buff it completely. Baby shampoo is a fine backup, especially if you already have some around. The potato is a party trick, and hand sanitizer is a waste of time.
But for reliability, clarity, and staying power, a purpose-built anti-fog product still wins. The hacks get you through a morning. The store-bought stuff gets you through a season.