Posted on 03 Oct 2011 15:03
What Causes Little Holes in Feet?
Pitted Keratolysis is an infection of the skin of the feet caused by a bacterial infection. Excessive sweating and tight, unventilated shoes can predispose you to this condition. The primary symptoms of this foot infection are bad foot odor and shallow pits on the bottom weight-bearing (plantar) surface of the feet. Most people describe this as "little holes on the bottom of my feet." However, it is their smelly feet that leads most people to seek treatment since there are rarely any other symptoms. Redness, soreness, and itching of the feet are also possible. This infection rarely occurs on the palms of the hands.
Causes, Symptoms, and Features of Pitted Keratolysis
Pitted Keratolysis, also known as Keratoma sulcatum is caused by excessive moisture due to sweating (hyperhidrosis) and a bacterial overgrowth of a variety of Corynebacterium species. Kytococcus sendentarius (or "micrococcus"), Dermatophilus congolensis, and some species of Actinomyces have also been identified as causes.
This malodorous foot infection is common among the military, and was first described in British troops in colonial India. It was also a big problem for American troops in Vietnam. However, it affects people worldwide, being more common in the tropics.
The key problem is softening of the soles of the feet caused by the moisture of excessive sweating. Sweaty feet that are not allowed to dry out, because of being enclosed in moist socks and shoes, combined with improper hygiene, allow diptheroid conrynbacterium to multiply and release keratolytic (keratinase) enzymes which eat little holes or pits in the outermost "horned" layer of the skin, called the stratum corneum. This layer consists of dead skin cells which are present as a barrier to protect the underlying skin from dehydration, infection, etc. Most often, it is the thickest parts of the feet that are involved, the heel and the area just under the toes, called the metatarsal region.
Those who must wear tight-fitting shoes and are prone to having their feet sweat or otherwise become wet are prone to pitted keratolysis. It is thus common among athletes, industrial and construction workers, soldiers, and anyone working in water. It is also possible from the frequent use of swimming pools and spas.
Pitted keratolysis, Large Lesions
Typically, the principal clinical finding is multiple small pits in the stratum corneum, about 2 to 5mm in size, which look like they were neatly punched out by a biopsy punch. The bottoms of these pits are lined with bacteria and sometimes they have a discolored or dark border. The skin may also be white and swollen in small areas. There may also be redness around the edges of the infected areas and smaller lesions may sometimes coalesce together to form larger erosions. Usually, besides the annoyance of smelly and unattractive feet, there are no other symptoms, although those that must walk for long periods of time may experience pain and itching.
Home and Over-the-Counter Treatment and Prevention
Pitted keratolysis can be treated with over-the-counter 5% or 10% benzoyl peroxide. Topical antibiotics such as erythromycin, mupirocin, or clindamycin are also used. These are applied once or twice daily.
The first thing to do is begin avoiding warm, damp conditions which cause and exacerbate the infection. If you are prone to sweaty feet and you must work under hot conditions in heavy foot-wear, you cannot possibly avoid this at all times, but it is certainly possible to take some helpful steps.
To prevent the infection and to help with treatment, the feet should be thoroughly washed and dried often. Simple washing and drying will help, but you can also use an antibacterial solution or soap, such as a benzoyl peroxide wash or other antibacterial wash, along with twice daily use of a 10% benzoyl peroxide gel, if necessary. If desired, use a hair dryer to dry the bottom of the feet after washing. Wear absorbent cotton or synthetic socks and change socks often. Synthetic liner socks worn underneath cotton socks can help wick moisture away from the feet. Carry extra socks with you to work or play, if necessary, and change them several times throughout the day. Also, foot powder can be used inside your socks to help absorb moisture. Expose your feet to air as often as possible. If you have opportunities during the day to remove your shoes and socks and air out your feet, then do so. When you get home, take your shoes off and allow them to dry.
Do not always where the same pair of shoes, so that each pair can dry as thoroughly as possible before being worn again. A good rule of thumb is 24 hours between wearings. Stay barefooted when possible, except perhaps for a pair of flip-flops or other open foot-wear. The simple habit of not wearing shoes unless absolutely necessary can go a long way towards clearing up and preventing the condition. Once the infection is cleared maintain the dry-feet habits and continue to wash and dry the feet thoroughly each day. If these measures fail to clear you infection within one to two weeks, see your doctor, who may prescribe other topical antibiotics.
Those who are prawn to excessive foot sweating may want to use antiperspirants on the bottom of their feet. You can use standard, over the counter antiperspirants for this but if they fail, even stronger prescription options are available such as Drysol or Xerac Ac. These are topical aluminum chloride hexahydrate solutions that work very successfully to control excessive sweating. Use these according to your doctor's directions. They should be used at night and washed off in the morning and they are NOT to be used with other over-the-counter antiperspirants. Check manufacturer's directions for all such products.
1. Landry, Gregory L., and David T. Bernhardt. "Dermatological Pathologies." Essentials of Primary Care Sports Medicine. Champaign, IL: Human Kinetics, 2003. 103.
2. Braun-Falco, Otto. "Chp. 4: Bacterial Diseases." Dermatology. Berlin: Springer, 2000. 168.
3. Elston, Dirk M. "Bacterial Infections." Infectious Diseases of the Skin. Washington, D.C.: ASM/Manson Pub., 2009. 19.
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