There’s nothing more frustrating than having foggy goggles.

Fogged-up lenses disrupt your rhythm and flow and restrict your vision, and it’s super annoying.

Whether you’re training, enjoying a leisurely swim or in the middle of a race there is no good time for foggy goggles.

To get to the bottom of this swimmer’s lament, we have researched the causes of foggy goggles and taken advice from the swimming community to find the best remedies to prevent your goggles from fogging.

Why do your goggles fog up?

There are multiple different reasons why your goggles might fog up but the science behind the main reason why your goggles are fogging up is surprisingly simple.

It all comes down to the temperature difference on either side of the goggle lenses; the side that sits on your face and the side that’s in the water.

Research has found that when the air inside your goggles is warmer than your goggle lenses, warm air molecules hit the cooler lenses and condense into water molecules which then causes your goggles to fog.

It is the same reason why people who wear glasses experience their lenses fog up when they open the oven or leave an air-conditioned building out into the warmer outside air.

While you might not feel it, when you swim your body can heat up quickly regardless of the water temperature, which can create a temperature imbalance, causing your goggles to fog.

Apart from this scientific answer, there can also be issues deriving from the anti-fog treatment many goggles have applied. These include:

How to prevent your goggles from fogging

Almost all goggles these days are sold as ‘anti-fog’ but that doesn’t necessarily mean that they will never fog for their lifetime.

What the ‘anti-fog’ means is that the inside of the goggle lens has been treated with a silicone-type film that helps repel water from the lens causing it to run off rather than form a mist/fog.

Over time, this anti-fog treatment is broken down, usually by repeatedly wiping with your finger. For ocean swimmers, this is compounded by the presence of tiny sand granules in the water which act like sandpaper on the lens.

If you’re finding your goggles are starting to fog up, either due to foggy-goggle-science, or you’ve simply worn out the anti-fog, there are several tried and tested solutions – as reported by ocean swimmers – that you can try to minimise the fog.