Used Shoes

I recently received a request to review an app that allowed people to sell their used shoes. In this case the app was specific to women’s shoe, but I have seen other solutions/sites for this same purpose for either gender. And, of course you can buy used shoes from eBay as well as some fashion forums.

This is sometimes referred to as “thrifting” and can extend to garage sales, estate sales and of course thrift shops. The idea is to buy quality made shoes for a fraction of the retail cost.

Unfortunately, unlike most other items you can buy used and get some utilitarian function out of, shoes are very physically intimate. Although not quite the same as buying used underwear, used shoes will have bacteria in the leather that was introduced by someone else. All leather has some degree of bacteria, if it has been worn.

bacteria

The main source of bacteria in used shoes is due to foot sweat. While some people sweat very little through their feet, other sweat quite a lot. The average foot has about 125,000 sweat glands with the majority being located in the sole and ball of the foot.

Sweat itself is odorless, but it creates a beneficial environment for certain bacteria to grow and produce bad-smelling substances. These bacteria are naturally present on our skin as part of the human flora
Brevibacterium is a genus of bacteria that is extensively present on the human skin, where it causes foot odor. The familiar odor is due to Sulphur containing compounds known as S-methyl thioesters.

Propionic acid (propanoic acid) is also present in foot sweat. This acid is a breakdown product of amino acids by Propionibacteria, which thrive in the ducts of adolescent and adult sebaceous glands. The similarity in chemical structures between propionic acid and acetic acid, which share many physical characteristics such as odor, may account for foot odors identified as being vinegar-like. Isovaleric acid (3-methyl butanoic acid) is the other source of foot odor.

The acids in the various bacteria slowly break down the amino acids in the collagen proteins that the leather is composed of. This process happens quicker with the presence of water moisture (like sweat).
It is not a question of if there is bacteria in the leather of used shoes, it is simply a matter of how much and how active.

The second concern with used shoes is the shaping that has taken place in the insole foot bed and the leather shoe upper.

Most men’s dress/business shoes have a mid-sole (between the insole and the outsole) that is typically made of thick cardboard (<$200 shoes), corkboard composite, or thick leather. The insole is then laid (and sometimes glued) on top of the mid-sole. Over time, as the shoe is worn, the insole and the mid-sole will begin to compress when they receive pressure from the toes, ball of the foot, and the heel. Since each person’s foot is unique to everyone else, the compression patterns will be as well. Insole-worn

It will take a while for these compression patterns to be created, and the time will depend on a number of factors like how often the shoes are worn, length of rest periods between being worn, the weight of the person, how much the person’s feet perspire, the quality of the materials in the mid-sole and the insole, and so on.

Because it takes a while to create these compression patterns it also takes a while to create new compression patterns. Unfortunately, because the compression patterns already exist (to one degree or another) in a used shoe, your bone structure (toes, ball of your foot, and heel) will be pulled into the existing compression patterns, much like tires into the ruts of a road.
This can be mitigated to a large degree by replacing the outsole with a new outsole, but it will still have a tendency to compress into the existing compression patterns in the mid-sole.

The shoe upper will have also formed to the shape of the previous owner’s foot. And on contact points where the upper touches the foot, even a single millimeter of give can make the difference between comfort and tired feet at the end of the day.

The leather upper can be stretched in the proper placed for the new owner, but the stretch points created by the previous owner do not go away.
For me, I simply cannot find any value in buying used shoes.