Pitted keratolysis (PK) is a superficial bacterial infection affecting the outermost layer of skin on the soles of the feet. It is characterized by distinctive small depressions or “pits” and a notably foul odor. PK is considered a common foot dermatosis, particularly among individuals who frequently wear occlusive footwear, such as military personnel or athletes. These individuals face an increased risk due to the creation of a perpetually warm and moist environment. The infection is also more prevalent in hot, humid climates and among people who experience excessive foot sweating (hyperhidrosis).
Appearance, Symptoms, and Commonality of Pitted Keratolysis
The most recognizable sign of Pitted Keratolysis is the presence of numerous small, crater-like indentations on the skin of the soles, concentrated on weight-bearing areas like the heel and the ball of the foot. These pits typically measure 1–7 millimeters in diameter, sometimes coalescing to form larger, irregular erosions. The lesions become significantly more pronounced and visible when the feet are wet, often appearing as whitish or grayish patches.
The symptom that most often prompts a person to seek help is a distinct, unpleasant odor, referred to medically as bromodosis. This strong smell is a direct result of the bacterial activity on the foot. While the pits themselves are usually asymptomatic, some people may experience mild tenderness, a burning sensation, or itching when walking.
PK is widely distributed globally, affecting all age groups, though it is more commonly observed in men than women. It is not contagious, but the warm, damp conditions created by excessive sweating are a major risk factor. This susceptibility helps distinguish PK from common fungal infections like Athlete’s Foot, which presents with different symptoms, such as scaling and intense itchiness.
Understanding the Bacterial Causes and Risk Factors
Pitted Keratolysis is caused by the overgrowth of specific bacteria that thrive in moist, alkaline environments on the skin. The primary culprits are species belonging to the genus Corynebacterium, though others like Kytococcus sedentarius and Actinomyces are also implicated. These bacteria flourish in conditions created by hyperhidrosis and the prolonged wearing of non-breathable, occlusive footwear.
The bacteria release proteinase enzymes that actively digest the keratin protein found in the stratum corneum (the outermost layer of the skin). This enzymatic breakdown process physically creates the characteristic small pits or tunnels in the skin’s surface. A byproduct of this bacterial metabolism is the production of sulfur compounds, such as thiols and sulfides, which are the source of the intense, foul odor associated with PK.
Risk factors that increase the likelihood of developing this infection include living in tropical or humid climates, having poor foot hygiene, and underlying conditions like diabetes. The combination of sustained moisture, warmth, and an alkaline skin surface creates the ideal microenvironment for these bacteria to proliferate. The goal of management is therefore directly related to disrupting this bacterial habitat.
Effective Treatment and Prevention Strategies
Treatment for Pitted Keratolysis primarily focuses on eradicating the bacterial infection and controlling the excessive moisture that allows it to flourish. Topical antibiotics are the first-line treatment, such as clindamycin or erythromycin, applied directly to the affected soles twice daily for a few weeks. Antiseptic agents like benzoyl peroxide gel may also be used, sometimes alone or in combination with topical antibiotics, to help reduce the bacterial load.
Preventing the recurrence of PK relies heavily on rigorous moisture control and hygiene practices, which must be maintained long-term. Feet should be washed daily with an antibacterial soap and dried completely, paying careful attention to the skin between the toes. Using an antiperspirant formulated for the feet, such as those containing aluminum chloride, can significantly reduce hyperhidrosis and inhibit bacterial growth.
It is advisable to wear moisture-wicking socks, such as those made from wool or synthetic fabrics, and change them immediately if they become damp. Footwear rotation is also recommended, allowing shoes to air out completely for at least 24 hours between uses to ensure they are dry. Avoiding prolonged use of tight or occlusive footwear helps prevent the warm, damp conditions that trigger bacterial overgrowth.