The appearance of numerous small, circular indentations on the soles of the feet can be unsettling. While the skin naturally contains sweat pores, these specific shallow depressions are often a sign of a superficial bacterial skin infection. This common dermatological condition is medically known as Pitted Keratolysis (PK). PK is highly treatable, but understanding its cause and the factors that allow it to thrive is necessary for resolution.
Identifying Pitted Keratolysis
Pitted Keratolysis is characterized by small, crater-like holes appearing primarily on the soles of the feet, especially in weight-bearing areas like the heel and ball of the foot. These pits are shallow and circular, typically measuring between 1 and 7 millimeters in diameter. The depressions may overlap to form larger, irregularly shaped areas of erosion on the skin.
The pitting becomes significantly more noticeable when the feet are wet, often giving the skin a macerated or slimy texture. While the pits are usually painless, the most distinctive symptom is a foul, pungent odor, medically known as bromodosis. This odor results directly from the bacterial activity within the pits.
The presence of the pits, sometimes accompanied by a brownish or greenish hue, is often sufficient for a clinical diagnosis. Distinguishing these lesions from normal sweat pores is straightforward due to their larger size, “punched-out” appearance, and concentration in pressure zones. Less commonly, some individuals might experience mild itching or a burning sensation when walking.
Understanding the Cause
The characteristic holes in Pitted Keratolysis are caused by an overgrowth of specific Gram-positive bacteria that colonize the outermost layer of the skin, the stratum corneum. The primary culprits are species of Corynebacteria, though Kytococcus sedentarius and Dermatophilus congolensis are also frequently implicated. These organisms are naturally present on the skin but become problematic under certain environmental conditions.
The bacteria thrive in a warm, dark, and excessively moist environment, typically created by hyperhidrosis, or excessive sweating of the feet. Wearing occlusive footwear, such as rubber boots or non-breathable athletic shoes, traps moisture and heat, providing an ideal habitat for bacterial proliferation. Once established, the bacteria produce enzymes called proteinases or keratinases.
These enzymes actively break down the keratin protein of the stratum corneum, creating microscopic tunnels and erosions in the skin’s surface. The strong odor is a byproduct of this process, resulting from the bacteria metabolizing the keratin and producing sulfur compounds like thiols and sulfides. This combination of excessive moisture and bacterial enzymatic activity creates the specific crater-like depressions.
Clearing the Infection
Treatment for Pitted Keratolysis focuses on eliminating the causative bacteria and aggressively managing foot moisture. Topical antibiotics are the first line of medical intervention due to the superficial nature of the infection. Healthcare providers commonly prescribe agents effective against Gram-positive bacteria, such as clindamycin 1% or erythromycin 2% to 4% solution or gel.
These topical treatments are typically applied twice daily for two to four weeks to ensure the bacterial load is cleared. Other effective options include mupirocin 2% ointment or fusidic acid cream, which directly target the organisms. Antiseptic washes or gels, such as benzoyl peroxide, may also be used alone or with antibiotics to reduce the bacterial population.
If the condition is persistent, severe, or the diagnosis is uncertain, a consultation with a podiatrist or dermatologist is recommended. Professionals may prescribe medical-grade antiperspirants containing aluminum chloride to control underlying hyperhidrosis. Addressing the excessive sweating concurrently with the bacterial infection is necessary for successful resolution and long-term prevention.
Preventing Recurrence
Long-term management requires hygiene and lifestyle adjustments focused on keeping the feet dry and aerated. The most significant change involves minimizing the time feet spend in warm, moist environments by avoiding prolonged use of occlusive footwear. When shoes must be worn, selecting models made from breathable materials is recommended.
Key Preventative Measures
- Change socks immediately if they become damp, using moisture-wicking synthetic materials or absorbent cotton.
- Alternate between at least two pairs of shoes daily, allowing each pair 24 to 48 hours to dry completely.
- Apply an antiperspirant, often one containing aluminum chlorohydrate, to the soles of the feet to reduce sweat production.
- Use antiseptic or medicated foot powders daily to absorb excess moisture.
- Wash the feet twice a day with soap or an antiseptic cleanser and thoroughly dry them, especially between the toes.
These consistent routines are the most powerful tool for preventing the return of Pitted Keratolysis.