Technological advances in orthotic materials can help decrease the problems and embarrassment associated with hyperhidrosis

Our feet have more sweat glands per inch of skin than anywhere else on the body. In fact, there are approximately 250,000 sweat glands in a pair of feet that excrete as much as half a pint of moisture each day.¹ When a patient has excessive foot moisture —hyperhidrosis— the feet will produce more than a cup of fluid. Several problems can develop: the skin will be susceptible to breakdown and damage, local and systemic infections may develop, and strong odors indicate the unhealthy state of the feet.

Don’t Sweat the Small Stuff
Several factors are involved in regulating the amount of moisture produced by the feet. An overactive thyroid or an infective state can raise the metabolic rate and cause a generalized increase in sweating. Since the sympathetic nervous system controls the perspiration rate in the feet and hands, autonomic imbalances and anxiety disorders will often result in more foot moisture. Most people have idiopathic hyperhidrosis, which indicates a lack of any identifiable causative condition. Work stress, competitive effort, and a modern, busy lifestyle can be the sources of the sympathetic stimulation that causes excessive moisture at the feet.

Sweat glands in the feet secrete all the time, not just in response to heat or exercise, as do sweat glands elsewhere in the body. Research has shown that foot sweating is not due to body overheating or elevated environmental temperatures.2 While sweating on the rest of the body surface is necessary for proper thermoregulation, the palms and soles of the feet do not participate in this function. One investigator found that in high temperatures, palmar and plantar sweating in relaxed subjects was negligible, while excited subjects produced considerable moisture on their hands and feet.²

When the feet are exposed to excessive moisture on a regular basis, several problems develop. Initially, there is a local effect on the skin, where various microbes take advantage of the altered environment to multiply. This process can result in a number of health problems and foot complaints:

Skin breakdown. Moisture that stays on the skin will eventually have a negative effect. Initially, this is usually noticed as a rash. Then blisters often develop, due to an increase in friction between a soggy sock and the damp skin.³ When the blister breaks down, it can become infected and painful. If not immediately treated, an infected blister can cause a life-threatening systemic blood infection, especially in diabetics and others with compromised immune systems. Long-term biomechanical irritation in combination with excessive moisture is a frequent cause of, or contributor to, persistent, painful calluses and plantar warts.

Foot odors. A consistently warm and moist environment is a perfect breeding ground for bacteria. In the feet, bacterial breakdown of surface proteins and fats results in a distinctive, foul smell. This condition (bromhidrosis) can be very difficult to live with.

Athlete’s foot and nail fungus. A fungal infection (dermatophytosis) of the feet and/or toenails is not limited to athletes, but is a rather common condition. The fungus can be picked up in any moist environment where an infected person has walked. When the feet dry, the fungus will die. But when the feet stay moist, the fungus can grow and spread. Once established, a foot fungal infection (tinea pedis) can be very difficult to eradicate and will eventually cause permanent deformity of the toenails. Foot dryness and moisture control are imperative in order to prevent these infections from becoming established, and also to deal with current fungal problems.

Best Feet Forward
There is no longer any reason for a person to suffer from the effects of foot sweating. Most recurring problems are due to inattention and ignorance of several important factors that interfere with normal evaporation of foot perspiration. When a small amount of time is spent caring for the feet, and proper choices of socks and shoes are made, most patients can easily control their foot moisture.

Foot hygiene includes daily vigorous washing followed by a thorough drying (including between the toes). Soaking in an astringent solution, such as strong tea (tannic acid) or vinegar water (acetic acid) aids the control of foot perspiration. For those with extremely sweaty feet, antibacterial soaps and antiperspirant sprays will aid in the drying effect.⁴ However, since antiperspirant sprays contain aluminum chloride, excessive use could result in absorption of aluminum, which has been linked to Alzheimer’s disease. Over-the-counter and alternative fungal controls (such as tea tree oil) may help some people. In more severe cases, topical prescriptions or even systemic fungicides—which have many side effects—or anticholinergic medications may be necessary to control a long-standing problem.

Socks made of natural materials, such as cotton and wool, help the feet breathe, while polyester and nylon socks and hosiery should be avoided. Some of the newer materials, such as olefins and acrylics, have even better wicking capabilities than natural fibers, and make better sport socks. Shoes should be made from breathable materials, such as leather, or have a mesh upper. Wearing sandals and going barefoot are even better, but not always practical. Insoles that contain charcoal are often only partially helpful, since they do nothing to control moisture, only odor. Socks should be changed at least daily, and shoes should be allowed to dry thoroughly, at least 24 hours, before they are worn again.

When a patient needs biomechanical support, yet has a problem with excessive moisture, orthotic selection is more limited, and has to be carefully considered. Custom-fitted sandals with biomechanical corrections built in are useful. For patients with sweaty feet that need orthotics, leather tops often are better than the newer viscoelastic materials, which do not breathe well. However, leather does not absorb shock as well as the viscoelastics. When a shock-absorbing benefit is needed, one possibility is synthetic material, which is porous (holes in the upper layer). This improves airflow and is very light.

New materials that use wicking to pull sweat away from the foot surface is one of the best solutions for controlling foot moisture while providing the necessary support of an orthotic. When an orthotic contains one of these materials, it is able to control most cases of hyperhidrosis, and normal foot moisture is handled efficiently.

John K. Hyland, DC, DACBR, DABCO, CSCS, consults, advises, and trains on the concepts of spinal rehabilitation. He has also served as director of several chiropractic rehabilitation practices for the past 7 years and works with the US Figure Skating Association. Hyland can be reached at 303-465-9158.

References
1. American Podiatric Medical Association. Answers to frequently asked questions on feet and podiatric medicine. Available at: www.apma.org/faqgeneral.html. Accessed March 7, 2002.
2. Kerassidis S. Is palmar and plantar sweating thermoregulatory? Acta Physiol Scand. 1994;152:259–263.
3. Subotnick SI. Sports Medicine of the Lower Extremity. New York: Churchill Livingstone; 1989:220.
4. Darrigan A, Reynolds K, Jackson R, Hamlet M, Roberts D. Efficacy of antiperspirants on feet. Mil Med. 1992;157:256–259.