New perk: Easily find new routes and hidden gems, upcoming running events, and more near you. Your weekly Local Running Newsletter has everything you need to lace up! Subscribe today.
Did you know that sweat itself doesn’t smell? The odor you find in your running shoes actually comes from the chemical process of bacteria on your skin breaking down acids in your sweat. Though the sweat glands in your body work differently (like those in your arm pits vs. your feet, for example), the process of breaking down acids is the same, leaving behind some amount of odor.
In total, the human body has between 1.6 to 5 million sweat glands. But do you want to guess which area has an abundance? That’s right, the sole of the feet (along with the palms of the hands) contain the greatest concentration of sweat glands with each foot containing 600 to 700 per square centimeter.
So it’s no wonder when all that sweat and bacteria get trapped in our running shoes and socks that our shoes retain the smell after going unwashed day after day. On the other hand, our feet and socks get washed and disinfected regularly.
“Just as with all other organisms, bacteria need fluid to thrive, and your foot sweat does that job perfectly,” explains Sara Landvik, who works as a science manager at Novozymes, a biosolutions company, and is an expert in bacteria and other microorganisms.
Our skin is covered with bacteria, including staphylococci, micrococci, and corynebacterium—and that’s quite normal. When your feet sweat, corynebacterium and micrococci break down the sweat into a fatty acid called isovaleric acid, which causes the smell in your running shoes.
But bacteria can do much more than make your shoes smell—they can do good things, too. They are extremely important in ecosystems, where they are crucial to maintaining life and breaking down materials, such as plants. Today, bacteria are used as a natural fertilizer in agriculture, for the production of flowers, vegetables, and crops, such as soy. Microbial solutions protect crops against diseases and help plants grow better.
Deodorant companies have even started selling probiotic deodorants as a way of promoting the growth of good bacteria that don’t stink while thwarting the malodorous ones. (Though, the research behind this kind of microbiome magic is still in the early stages.)
RELATED: How to Choose Shoes for Wet, Rainy Races
And while we have a host of products and tactics to keep our pit odor under control, many of us don’t pay nearly enough attention to our feet. Here are five ways to keep the bacteria in your running shoes under control.
How to Get Smell and Bacteria Out of Shoes (And Keep It Out)
Deodorizing shoes is not just important for maintaining a social life, but it is also a foot health practice. Remember, smell comes from the combination of bacteria and sweat. According to an article in the Journal of Athletic Training, athletes are more susceptible to bacterial and fungal infections on their feet. And while bacteria-rich shoes are not the only cause of infections like athlete’s foot, giving them some TLC is just one more way to keep feet healthy.
1. Freeze Them
Put your shoes in the freezer to reduce the amount of bacteria and some odor. Although it’s been disproven that freezing textiles kills all bacteria, it does kill some. If you choose to go with this method, however, we recommend putting your shoes in some sort of plastic bin, container, or plastic bag to prevent your shoes from coming out smelling like frozen taco meat (and to keep your frozen taco meat from smelling like feet). That goes for any other foot product you store in your freezer, like YogaToes or special ice packs.
2. Keep Them Dry
Bacteria and microorganisms thrive in damp conditions, so keep your shoes dry by stuffing them with newspaper after a run. Storing shoes out in the sun has also been proven to be an effective method of drying and sanitizing footwear.
3. Rotate Which Shoes You Wear
If you’re able to invest in more than one pair at a time, try not to run in the same pair of shoes two days in a row. Giving your shoes at least 24 hours to dry out will prevent any scents from lingering.
4. Wash Them
Running shoes can and should be washed at least once in their lifecycle. Arya recommends washing running shoes once every two months. The brand website for the specific pair of shoes that you run in will provide the best advice for washing that pair without damaging them (such as hand washing versus machine washing).
These methods should work wonders on the everyday sweat that runners build-up, but if you have issues with chronic sweating (such as hyperhidrosis) or deal with fungal infections regularly, you may want to speak with a specialist.
RELATED: Racing Shoes: What You Need to Know
5. Neutralize the Odor
Because the smell in your shoes comes from isovaleric acid, you can neutralize it with an alkaline compound like baking soda. Sprinkle half to a whole tablespoon of plain baking soda into each shoe and leave them overnight. “Silica gel sachets can be kept in the shoe during storage and baking soda breathable pouches can also be kept inside to avoid smell,” says Preeti Arya, assistant professor of textile development and marketing at the Fashion Institute of Technology.
Or opt for a product designed to neutralize odors in shoes specifically. Here’s a look at some leading products available for neutralizing running shoe odors.
Foot Sense All Natural Foot And Shoe Powder
Foot Sense powder neutralizes odors both by reducing bacteria in your shoes and by adding natural scents, such as lemon powder and cinnamon bark powder. However, the powder does leave some residue, so runners who go sockless might not enjoy this product.
Remodeez Footwear Deodorizer
The Remodeez Footwear Deodorizer sits inside your shoes when you aren’t wearing them to help absorb left-over moisture while deodorizing the shoes with activated charcoal. The odorless deodorizers require monthly recharging in sunlight but if well cared for they can provide a year of shoe deodorizing.
Arm & Hammer Odor Defense Shoe Refresher Spray
Using an odor-defense spray on your shoes is fast. Shake the can, spray it in your shoes, and enjoy the baking soda spray will neutralize your shoe’s smell. The spray is lightly scented. For best results, allow the spray at least overnight to do its deodorizing.
Mini Moso Bag
These linen bags filled with bamboo charcoal offer a non-toxic, chemical-free solution to shoe deodorizing. Slip the bags in your shoes after running to keep your shoes fresh. Place the bags in direct sunlight monthly to recharge them and enjoy two years of deodorization.