Keep a few simple tricks in mind, and you can prevent your shoes from getting funky, and freshen them up if they're getting a little “ripe.”
Treat Your Leather Right
As a natural product, leather needs lipids to protect its grain structure and keep it from drying out. A quality leather conditioning treatment keeps your footwear from getting funky for a few reasons. First, it will keep your footwear from absorbing water. Wet leather encourages the growth of bacteria and fungi, which can generate some serious stink in short order. Second, well-treated leather is less likely to absorb off-odors from the environment. Warning: any effective leather conditioning treatment will darken your footwear. Try it out on an unobtrusive place first, like the back of the heel. I like the richer, darker look leather conditioners impart, but you might not.
Clean Your Leather
Every so often, use a soft, wet cloth to clean up the inside and outside of your leather footwear. Don't use a soaking wet cloth, or you'll risk saturating the leather and damaging it. You want it just damp enough to lift obvious dirt and grime. For seriously soiled kicks, use a gentle, non-detergent soap like Nikwax Footwear Cleaning Gel™ and a soft bristle brush. Either way, remove the insole prior to cleaning. When you're done, leave the insole out, open the shoe and leave it to dry in a warm place.
Store Your Leather Dry
Sweaty, stinky feet happen. After you're walked 10 blocks to a job interview in your sweet OluKai Walinos, your little piggies may feel a trifle damp. Don't make the problem worse by stowing them in a damp, dank closet. Store your leather footwear in a clean, dry, area with plenty of room for air circulation. Don't doom them to the closet. Show off your attractive shoes on a nice rack. Exposure to moving air and sunlight will help keep your shoes dry and smelling good. Use SocksThis advice obviously doesn't apply to sandals (unless your nerd rating is off the chart). A sock provides an important barrier between your feet and your shoes. It prevents your feet from transferring natural oils, sloughed skin, and bacteria to your footbed and the inside walls of your shoes. Even if your feet smell sweet, these natural debris will accumulate in your footwear and become food for fungi and bacteria. More importantly, socks wick away the nearly one liter of perspiration your feet can produce in a day. No socks? This moisture is going right into your leather footwear, and in short order, it'll be funkier than a George Clinton B-side. Unfortunately, you may not have read this article prior to your footwear purchase, and now you're dealing with a case of the stinky foot. All is not lost! There are a few ways to salvage all but the funkiest shoes:
Eradicate the Fungus
If you've got seriously rank footwear, you may be harboring a fungal infection. Even if you don't have “athlete's foot,” there are many species of non-pathogenic fungus can colonize your footwear, leading to sour or funky odors. Purchase a generic “Foot and shoe powder spray” that contains at least 1% Tolnaftate. If you've got insoles, take them out, and spray the inside of the entire shoe, as well as both sides of the insole, generously. Let them dry for an hour in a warm, dry place and repeat the treatment once more.
Swap the Insole
Sometimes, stinky footwear is actually just a stinky insole. Because it's in direct contact with the moistest part of your foot the most often, insoles really get a dousing of sweat. Replace your insole with an after-market product that fits your shoe, and that is a similar volume to the factory insole. If you add a new insole that's got a high arch, or a lot of additional padding, your shoes might not fit as well, so take your stanky old insoles to the store when you buy a new pair.
Bring Out the Big Guns
Let's say you've got a pair of shoes so rank, so terrible and awful, that they make flowers die and babies cry. Let's say that, beyond all reason, you want to keep them. Perhaps they make you remember that trip to Hawaii, or the night you went out dancing and met your spouse. Fear not — there is a nuclear option for the seriously funky footwear. First, remove your insoles, and scrub your shoes inside and out with a damp sponge on to which you've sprayed a generous dose of tea tree oil. Allow the shoes to dry in a warm (not hot!), sunny place, propped open with the insoles out. Then, pour an entire box of baking soda into two old socks. Place the soda-loaded socks into your shoes, and let them sit in a warm (NOT hot), dry place for a few days. Using this technique, I've rescued a few pair of stinky shoes too pricey or with too much sentimental value to part with.