Conway McLean, DPM, Journal columnist

Think, for just a moment, about your skin. You probably already do. From worrying about the appearance of our skin, to applying make-up, or worrying about a new mole, even lotion and moisturizer application, skin care and skin problems occupy a surprisingly large part of our time. Whether we consciously think about it or not.

There is no question skin care, when combined with the medical care of the problems associated, is a multi-multi-billion dollar industry. Dermatologic medicine alone totals over 10 in the US, 38 billion world-wide. The skin product market is valued at almost 180 billion. Make no mistake about it, skin care is about much more than looking good. For example, the incidence of malignant melanoma is rising and so is the resultant death toll.

Our skin has a multitude of critically important functions, some of which may not be obvious. Most people are aware of its necessary role in preventing water loss, which is why burns are so deadly. But skin has vital work in maintaining our immune system, and reducing the risks of invading microorganisms. It also provides protection against many forms of physical damage, whether it is stepping on a rock or “simple” pressure from shoe gear.

Naturally, our skin is prone to many diseases and conditions, from psoriasis to fungal infections. Perhaps the most common is felt to be a normal finding, and without repercussions. Calluses are the subject referred to. Technically labeled keratosis, these are a natural and predictable consequence of pressure or irritation of the skin, specifically the layer of skin called the corneum. This is the outermost layer, the one we are shedding every minute of the day. And the one responsible for over-growing and thickening, the result being callus formation.

Although you may not have thought about it (and trust me, I have), callusing is simply a defensive mechanism. The skin is attempting to protect the body from physical stress, be it from a shoe a half size too small or a toe bending excessively. There a tremendous variety of factors determining how much callus a person makes, with hereditary being the biggest. Skin hydration is a significant one, meaning the use of a moisturizer has actual health benefits.

Callus development is incredibly common in the feet, where the skin is unlike anywhere else on the body. On the sole of the foot, there are two extra layers, a necessary defensive mechanism. Being bi-pedal has so many ramifications, and tremendous stresses to the skin of the feet is one. Calluses are often benign entities, nuisances only, eliciting no pain. But time changes everything, and as our circulatory system declines over the years, skin becomes more fragile, nerves pressured for years are increasingly excitable. Calluses once an afterthought often turn into a source of pain

This process of skin thickening has more implications than just pain. Fibrosis is scarring of the deeper layers of skin and can be intensely painful with pressure. Skin breakdown can also result at these sites. Alternatively, ulcers can develop when skin is thin and unhealthy, as in those with arterial disease. Those with heart disease are also prone to this common occurrence.

When in an area of greater pressure, like the ball of the foot, this pathologic process can lead to real morbidity. Those calluses that have formed on the bottom of the foot can interrupt blood flow to the living cells in the area. Those with diabetes often can’t feel the pain from recurrent, excessive pressure build-up resulting from callus production. Under all that callus, it’s common to find some degree of skin death, aka an ulceration. Depending on the severity of this gradual, insidious problem, infection can set in, requiring hospitalization, IV’s, and often surgery to clean out the infection. Amputations occur far too frequently, the product of a simple callus.

Prevention will go a long way towards preventing many of these callusing problems. How many of us are farsighted enough to care for them appropriately at an early, asymptomatic stage? Moisturizing the feet is a wonderful practice, although what is being used is important. Unfortunately, many less-informed citizens slap on your typical hand and face lotion, but these are relatively ineffective for the feet. Go thick and water-based (as opposed to a petroleum product). Studies show these generally to be more effective.

Some people need to take a more aggressive approach to skin hydration, with the addition of a keratolytic. This is a medicine which actively breaks down callused, thickened skin, although gradually, safely. When calluses have become a significantly painful problem, an occlusive technique can be utilized, in which the lesion is covered with an impermeable membrane (your basic plastic wrap) after applying a thick moisturizing cream. Typically this is kept on overnight, held in place with a sock.

If pressure to some area of the foot is the cause of so many problems, how best to alter this pathologic course of events? When the callus is on the bottom, reducing these forces may be achieved by altering the supporting surface, which is hard to do well with shoe modifications. Foot orthotics are the most scientifically prescribed and fit method, when properly done. It is possible to modify a prefabricated, over-the-counter device but this will never be as effective.

Surgical procedures are commonly performed to reduce the bony prominence, be it a bent toe or the head of a metatarsal bone bulging out the ball of the foot. All sorts of bumps can be found, with the infamous bunion being another candidate. The years of pressure from this particular type of prominence lead to thin, unhealthy skin over the bump, and when ulceration does occur, healing is excessively challenging.

The results are in, the polls performed, the studies tabulated. Calluses on the feet, be they on the toe, sole or heel, can be dangerous. There are a multitude of treatments, methods and approaches for minimizing the consequences of chronic skin pressure. These callus can be treated, and often should be, so see a specialist. There are consequences to calluses….. they just may not be today.