European footwear retailer size? has hit the lab to prove once and for all that rocking shoes without socks allows more germs to thrive compared with when you wear socks. Up to three times more, in fact. That's science.

Swab tests were run on the sole, upper, and insole of different sneakers worn in different environments to find out how bacteria grows on our kicks. The proof was in the proverbial (albeit disgusting) pudding, after the swab samples were transferred to petri dishes and left to grow for five days.

As Nike has reminded us via releases such as the Tom Sachs Mars Yard Overshoe and React Element 87, cork insoles are one way to battle bacteria, as the material is naturally antimicrobial, plus its built-in water resistance helps keep out mold and mildew. But what about the other materials used on kicks, and particularly on the insoles? Unfortunately, there's only one way to find out.

Check out the results of the tests below via shots of each petri dish and the study's main takeaways.

Canvas sneakers

When worn without socks, canvas shoes have the potential to cultivate three times more germs. If you don't believe us, compare the two insole petri dishes above. Holy hell.

Black sneakers vs. white sneakers

Black sneakers may be dirtier than they actually look, and can be hiding a wider variety of bacteria than white sneakers, which are typically cleaned more often because dirt is more visible on them.

At the gym

Sneakers that have been worn at the gym hold significantly fewer bacteria than you might expect. Your shoes might not smell the freshest after a solid gym session, but odor doesn't necessarily mean bacteria.

Beware of beaters

After a night of bar-hopping, your shoes will be teeming with bacteria, far more than shoes worn to the gym. You might want to take a closer look at those beaters you keep by the front door and maybe toss them in the washing machine after a night on the town.

To go along with this new study on sneaker bacteria, size? also put together a guide on how to clean your kicks. Check out the guide here, to ensure you don't end up with a chronic case of swamp foot.

For our guide to clean your sneakers, watch below.

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