Causes and Goals
Bacteria feeds on sweat, so wearing the same shoes all day for a few consecutive days doesn't give the footwear enough time to adequately dry. Although you can rotate a few pairs during the week, this isn't something everyone can afford to do. The goal therefore when combating shoe odor is to starve bacteria of its food source by keeping the interior of the footwear as dry as possible. If buildup has already occurred, the only other option is to kill the bacteria and start fresh.
Shoe blocks and stretchers are commonly made from cedar. In addition to providing a natural fresh scent, cedar is also highly absorbent. It's a good idea to store shoes with a few cedar balls from the first wearing to preclude bacteria buildup. Storing the shoes on an open shoe rack also helps the shoes to air out. Cedar bags and blocks are also available, serving the same purpose. You can take a few extra balls or blocks and place them in sweater drawers or anywhere wool is present, helping to ward away moths. Cedar shoe trees maintain the shoe's shape, while also imparting the wood's natural odor and drying elements.
During the summer, it's not uncommon to see men and women alike wearing leather shoes sans socks or hosiery. Perspiration from feet enters the leather directly, without any absorbing agent in between. One way to absorb excess moisture and knock down odor is to sprinkle foot or baby powder into the shoe, moving it around for even dispersion. Keeping a box of baking soda by your shoe rack helps pull away moisture, and you can sprinkle that into shoes if you don't have any foot powder. Stuffing shoes with newspaper helps the shoe keep its shape, while absorbing any sweat from the liner.
If cedar balls and baby powder aren't enough to keep shoe odor at bay, it's time to take more dramatic steps. Wetting a cotton ball with isopropyl alcohol and wiping the inside of leather shoes should instantly kill any bacteria. However, it also dries out the leather. After the alcohol dries, follow up by rubbing the shoe inside and out with a leather conditioner to return essential moisturizers to the leather. If the shoes happen to be canvas instead of leather -- and fairly durable as well -- you can throw them in the washing machine on a gentle cycle with warm water. Dry them on a rack with balled-up newspaper -- not in the dryer, as this will cause the material to pull away from the rubber sole. Dumping a scoop full of kitty litter in freshly-worn shoes is great for absorbing moisture and odor, which is what it's made for in its conventional use. Place the kitty litter in a nylon stocking to prevent a mess inside the shoe