Have you seen a swimmer spit in their goggles right before swimming? I used to think this was gross. But there’s a very good (scientific) reason for this.
Swimmers spit in their goggles because saliva is a natural surfactant that keeps goggles from fogging. Surfactants are substances that reduce the surface tension of a liquid. Anti-fogging products are for sale, but saliva remains one of the best ways to keep goggles from fogging.
I thought this was fascinating. I did some more research and found the following information helpful. I hope you do too.
Why do swim goggles fog up?
Fogging in goggles comes from condensation on the inside due to sweating. Tiny water droplets form because of the difference in temperature between the inside and outside of the goggle.
Fog is simply tiny drops of water close together. Each drop is spherical, so vision is distorted when looking through it.
This is the same phenomenon that happens when a car windshield get’s foggy or when your glasses fog up after coming in from the cold.
In a car, we turn on the defogger which blows air to dry the water droplets. With glasses, we simply wipe the moisture away with a cleaning cloth.
But we can’t do either of these while swimming.
So we spit in them to keep goggles from fogging in the first place.
Why does spit keep goggles from fogging?
Saliva (spit) is a natural surfactant our bodies make. Spit helps in digestion.
According to Wikipedia, “surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid.”
We know that fog is just tiny spherical droplets of water. They form that shape because of the surface tension of water.
With their shape, light gets distorted when looking through the drops.
Water is clear. So if we could flatten out the little spheres, we’d be able to see a lot better.
The surfactant, in this case saliva, reduces the surface tension of the drops. And they smooth out on the inside of the goggles.
Is spit bad for your eyes?
Saliva (spit) can have bacteria that is not good for your eyes.
Only use a small amount of spit. Just enough to be able to cover the inside surface.
When you spit in your goggles, use your finger to rub the saliva around. You want a thin, smooth coating to prevent fogging.
Make sure your fingers are clean so you don’t smear dirt or oil on your goggles.
Importantly, do NOT rinse your goggles with pool water after spitting in them. Doing so will just wash away the saliva and allow the goggles to fog again.
The benefit of saliva is you don’t have to worry about running out!
How else to keep swim goggles from fogging
What other kinds of surfactant are available? Here are a few.
Dish detergent, shampoo, or soap
Dish detergent is a surfactant. So is soap.
For goggles I would not recommend normal soap because it irritates your eyes. You don’t want to have to stop mid-lap because your eyes are burning.
A mild dish detergent, like Dawn, or a shampoo like Johnson’s Baby Shampoo can work well.
Just put a small amount in your goggles and smooth it with a soft, clean cloth. Again, do NOT rinse the goggles before putting them on or you’ll lose the anti-fog protection.
Commercial anti-fog sprays
There are lots of anti-fog products on the market.
These surfactants work like saliva or dish soap to break the surface tension of the water droplets, but are formulated to last longer.
Before swimming you spray the inside of your goggles, then wipe the excess off with a soft cloth. Be careful not to scratch the surface of your goggles.
Anti-fog spray for goggles is typically sold in a small, one-ounce bottle (30ml). They range in price from $5 to $20 depending on the brand, bottle size, and formulation.
Just know that the chemicals used in anti-fog spray may be toxic. If you get the spray in your eyes you need to rinse them with clean water immediately.
If the environment and personal health are important to you, stick with saliva or dish detergent.
Don’t let foggy goggles keep you from swimming your best
It’s annoying to have to wipe your goggles every lap because they are fogging.
I see my daughter wiping out her goggles just before each race. She’s a sprinter, so she’s not in the water for long.
But if you’re swimming longer events I imagine you want to avoid foggy goggles so you can read the lap counter in the water.
There are quick and easy ways to keep your swim goggles from fogging up.
Use the best option for you that keeps them clear:
- Saliva – spit a little in your goggle and spread it in a thin layer to prevent fogging
- Disk soap/detergent – put a tiny drop and use a clean cloth to create a thin layer
- Commercial anti-fog spray – spray inside the goggle and wipe off any excess
Remember, with all of these options, DO NOT rinse your goggle out after application. You’ll just wash out the anti-fog protection.
I hope this was helpful. Thanks for reading!