July 13th, 2011
12:03 PM ET
Every weekday, a CNNHealth expert doctor answers a viewer question. On Wednesdays, it's Dr. Otis Brawley, chief medical officer at the American Cancer Society.
Question asked by Juliet from Kansas
My boyfriend's feet sweat and burn profusely. He washes them and changes socks/shoes several times a day. He's tried every athlete's foot remedy at doctor's advice, and nothing works. What could this be? He's very clean, doesn't have bubbles or blisters or anything unbecoming on his feet. He even warms his feet in front of a stove before putting socks and shoes back on.
Plantar hyperhidrosis is the medical term for excessively sweaty feet. It is a common problem and rarely linked to any underlying disease.
It can be a significant problem, interfering with a person's quality of life. Sweaty feet can become a breeding ground for bacteria and lead to significant foot odor as well as fungal skin infections that lead to a burning sensation of the feet.
The skin of the human foot can make more sweat per square inch than the skin of any other part of the body. This is because the skin of the foot has more sweat glands per square inch than the skin of any other body part.
Moisture accumulation is most commonly associated with heating of the foot and poor ventilation of the shoe. In addition, it is normal for dead skin cells to exfoliate or slough from the skin constantly.
The skin of the feet is no different from the skin of the rest of the body except that dead skin cells from the feet accumulate with sweat in a closed area. In this environment, fungi and bacteria that are usually present are able to grow and thrive. This overgrowth can lead to foul odors and burning.
Most foot fungi reside on the soles of the foot and between the toes. This is where one would expect most of the burning to be localized. Burning and itching of the feet is most likely due to skin infection with fungi.
This is more severe than the fungi simply being on the skin surface and is commonly referred to as athlete's foot or tinea pedis. The skin can look relatively normal to the untrained eye.
The patient might consider having a podiatrist verify the diagnosis. For many there will be benefit from weeks of treatment with a topical anti-fungal drug such as clotrimazole (sold under brand names including Cruex, Desenex and Lotrimin) or tolnaftate (whose brand names include Tinactin and Aftate). Some will need prescription oral anti-fungal agents such as ketoconazole (brand names Feoris and Nizoral) or griseofulvin (brand names Fulvicin-U/F, Grifulvin V and Gris-PEG).
Stinky feet are caused by overgrowth of bacteria. Interestingly, a skilled diagnostician can identify the type of bacteria from the smell. Cheesy smells are linked to specific types of bacteria, vinegarlike smells to others and rotten garbage smells to yet other bacteria.
Some people report that a change in diet, while not affecting sweating, can reduce foot odor. They recommend a diet lower in processed carbohydrates and higher in complex carbohydrates and higher in proteins.
Common measures should be taken to treat excessive sweating of the feet:
• Wash the feet daily with warm water and an antibacterial soap. Dry the feet thoroughly with a dry and soft cotton towel, especially between the toes.
• Use a shoe spray designed to reduce the smell and accumulation of bacteria and fungi. In severe cases, a trial of an underarm antiperspirant sprayed or applied to the feet is reasonable.
• Use foot powder to dry the feet.
• Wear thick socks, so they can absorb and wick away the moisture and help ventilate the feet.
• Use 100% cotton or 100% wool socks. Avoid, synthetic socks and stockings (polyester or nylon) as they can worsen the problem.
• Change socks several times a day.
• Wear shoes with adequate ventilation. Avoid plastic or nylon shoes. When not wearing shoes, let them air out in an area where dry air is circulating.
In patients who do not get enough benefit from the above, some podiatrists and dermatologists have used injection of onabotulinum toxin A, better known as Botox.
There are reports this therapy will reduce foot sweating from three months to a year before it needs to be repeated. Patients considering this therapy should have a good conversation with their doctors concerning the potential risks and benefits of this therapy.
The Food and Drug Administration has approved Botox for treating excessive sweating of the underarm but not for excessive sweating of the feet. Health insurance companies, therefore, may not pay for it.
Serious problems that can cause excessive sweating and burning of the feet include diabetes with diabetic neuropathy and peripheral vascular disease. A physician can easily exclude these diagnoses.
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