The Pro Bono Thinking Society

PBTS6: Leather Loafer of Indestructible Odor

Status: Complete

REPORT (updated February 3rd, 2012)

PBTS Project #6
Title: Leather Loafer of Indestructible Odor
Start Date: 11/18/11
Report Date: 2/3/12

I. Summary of the Problem
Problem submitted by the public:

Okay, I bought a pair of leather loafers the other day that now has an ungodly stank. I wore them without socks for a while and now they have a foot odor that just won’t quit. I have tried some solutions that haven’t done the job at all. I placed them in a ziplock bag and froze them over night…..No go…..I tried a pet stain removal spray….No go….Baking soda….No go….I can’t quite wrap my mind around this bacteria being indestructible. Please help with any new ideas…Thanks.

II. Initial Research
This is a problem almost all any of us can say we have dealt with, so discussion immediately began about the various ‘at home’ treatments each of us have used. However, as the original submission mentioned, most of these solutions just don’t work.

The first thing to do in figuring out how to properly attack a problem is to figure out what is causing it and luckily we have some microbiology expertise in house. Once we were all more clear on what was happening inside of the shoe, discussion and research moved forward more confidently.

III. The Cause of the Problem
In a practical sense, the obvious cause of the problem was not wearing socks. Feet, including toenails, are full of bacteria. Once you provide it with moisture, warmth and skin, the bacteria has the perfect environment to thrive. Socks would absorb and protect the shoe but without them, the bacteria are free to grow.

In a more scientific sense, the cause is specifically cheese bacteria. Something related to Propionibacterium which, when it isn’t making holes in Swiss Cheese, makes your feet smell. The bacterial ferments all the proteins it can in the shoe, some of which have amino-acids with sulphur built into them. It’s the volatile sulphur-containing by-products of this fermentation that our nose can detect in minute concentrations and interpret as ‘bad’. This has served us well for millions of years as a spoilt food detector.

IV. Why The Attempted Solutions Failed
The stinky microbial population that is the root cause of the problem is a tough enemy. Freezing kills some of the bacteria but they are tiny and crammed full of molecules which makes it hard for ice crystals to form inside of them. Once you combine that with the high growth rate, the problem will always come back once they thaw out.

A similar logic can be applied to pet sprays and foot powder. Once you have a shoe full of these things, you have to get rid of all of them or the problem will always return.

V. Recommended Solution
Our suggestion is sunlight and wind. UV light is a terrific disinfectant so place the shoes in as much sun as possible for 1-2 days. If the shoes have any kind of removable insoles, those should be removed and placed in the sun as well.

The shoes should be spread open and rotated occasionally so that the UV can irradiate as much surface as possible and, of course, they should be kept out of the rain. Exposure to UV light for more than 1-2 days could begin to take a toll on the leather so don’t forget about them.

The wind and fresh air will also help in drying and removing any odor.

Devices do exist to do the same job sunlight will do in sanitizing your shoe. We have no experience with such a device but the customer reviews are glowing.

VII. Preventing Reoccurrence
1. Socks
Wearing socks would be the easiest way to keep the bacteria from reestablishing itself in the shoe. SmartWool specifically are made to keep your feet dry and can be found in low-cut styles.

2. Extra Foot Care
If wearing no socks is not an acceptable option, and the feet tend to be sweaty, consider a foot bath and extra foot care. Keep toenails trimmed and clean and soak feet in a bath of hot, saturated salt solution. This can be made with a bag of sodium chloride (not calcium chloride) from any hardware store.

3. Cycle Wearing
Try to never wear the shoes more than one day in a row and let them dry and air out between wearings.

4. Lysol/Alcohol
While Lysol or alcohol will likely not defeat the problem in the long term, they could be used to temporary treat some of the symptoms and kill surface bacteria.

VIII: Final Thought
No treatment, short of shoe destruction, will completely eliminate bacteria in a shoe and you’ll always have them in and on your feet. Consider the ‘food/moisture/warmth’ tenet of biology. Deny one or more of these to the cells in your newly sun-exposed shoe and they’ll have a really hard time re-establishing themselves.

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BRIEFING (updated November 18th, 2011)

Submission from the public:
“Okay, I bought a pair of leather loafers the other day that now has an ungodly stank. I wore them without socks for a while and now they have a foot odor that just won’t quit. I have tried some solutions that haven’t done the job at all. I placed them in a ziplock bag and froze them over night…..No go…..I tried a pet stain removal spray….No go….Baking soda….No go….I can’t quite wrap my mind around this bacteria being indestructible. Please help with any new ideas…Thanks. “

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