What Causes Small Holes in the Skin
Pitted keratolysis is a bacterial skin infection that can cause small holes in the skin, mainly on the soles of the feet or palms of the hands

Pitted keratolysis is a bacterial skin infection that can cause small holes in the skin, mainly on the soles of the feet or palms of the hands. 

It is more common in people who live in tropical climates and frequently go barefoot or those who wear occlusive shoes.

What are the symptoms of pitted keratolysis?

Pitted keratolysis often causes similar symptoms to athlete’s foot and may include:

  • Crater-like pits in the top layer of the skin, each about 1-3 mm in diameter
  • Unpleasant odor that worsens when the skin is wet.
  • Excessive sweating
  • Pain or itching when walking
  • Occasional burning, stinging, or discomfort

If left untreated, the small holes in the skin can merge to form large lesions.

What causes pitted keratolysis?

Pitted keratolysis is caused by the following bacteria species:

  • Kytococcus sedentarius
  • Dermatophilus congolensis
  • Corynebacterium or Actinomyces

When these types of bacteria grow on the skin and secrete protease enzymes, they can cause the breakdown of keratin proteins in the superficial layer of the skin. As a result, sulfur compounds are formed, causing a strong odor and small holes in the skin.

What are the risk factors for pitted keratolysis?

Bacteria tend to thrive in moist environments. Conditions that can encourage bacteria to grow include:

  • Excessive sweating 
  • Tight-fitting socks or shoes
  • Diabetes
  • Advanced age
  • Compromised immune system
  • Lack of foot hygiene
  • Working in moist environments barefoot (e.g., pastures and paddy fields)

Other risk factors for pitted keratolysis include:

  • Not drying the feet thoroughly after bathing
  • Not wearing absorbent socks
  • Sharing towels

People with the following occupations may be more prone to developing the condition:

  • Athletes
  • Farmers
  • Sailors
  • Fishing workers
  • Industrial workers
  • Military workers

How is pitted keratolysis diagnosed?

Physical examination can help diagnose pitted keratolysis. Additional testing may include:

  • Dermoscopy to see the pits and pit walls
  • Wood lamp exam, which uses UV light to examine the skin (pitted keratolysis may cause coral-red fluorescence)
  • Potassium hydroxide preparation to help rule out the presence of a fungal infection

What are the treatment options for pitted keratolysis?

Treatment of small holes in the skin usually depends on the severity of the condition and may include:

  • Treating the underlying cause of excessive sweating
  • Topical hydrocortisone cream or clotrimazole ointments
  • Oral antibiotics to clear stubborn lesions
  • Antibacterial soap
  • Injectable botulinum toxin
  • Antiperspirant with aluminum chloride

First-line treatment typically includes topical antibiotics. Oral administration of erythromycin is recommended in resistant or severe cases. With the right treatment, the infection and odor should go away within a few weeks.

How to prevent pitted keratolysis from coming back

To avoid recurrence, basic hygiene guidelines should be followed:

  • Wear open footwear whenever possible
  • Avoid wearing shoes that are not breathable and cause the feet to sweat
  • Wear moisture-absorbing insoles and keep a few pairs on hand to rotate regularly
  • Wash the feet twice a day with soapy water or antiseptic water
  • Use a 20% aluminum antiperspirant 
  • Wash socks in temperatures above 140 F to kill bacteria
  • Change socks daily

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Medically Reviewed on 2/9/2022
References
Image Source: iStock Images

WebMD. What Is Pitted Keratolysis? https://www.webmd.com/skin-problems-and-treatments/what-is-pitted-keratolysis

Oakley A. Pitted keratolysis. DermNet New Zealand. https://dermnetnz.org/topics/pitted-keratolysis

Fernández-Crehuet P, Ruiz-Villaverde R. Pitted keratolysis: an infective cause of foot odour. CMAJ. 2015;187(7):519. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4401600/