Erosio interdigitalis blastomycetica is a superficial yeast infection affecting the skin between adjacent fingers or toes. Although classically described on the hands, it also occurs in the foot, where it represents a form of interdigital candidiasis. The condition is usually associated with Candida albicans, an opportunistic yeast that thrives in warm, moist environments. Despite its historical name, it is not caused by Blastomyces, the fungus responsible for blastomycosis. Recognising this distinction helps prevent confusion about its cause, significance, and treatment.
The interdigital spaces provide favourable conditions for infection when moisture accumulates. Closely apposed toes, enclosed footwear, excessive sweating, and inadequately dried feet create a humid environment. Prolonged moisture softens the outer skin layer, producing maceration and weakening its protective barrier. Friction between neighbouring toes further damages this vulnerable surface, allowing Candida to proliferate. Consequently, the disorder reflects an interaction between microbial growth and local environmental conditions rather than simply exposure to a fungus. Persistent dampness also explains why medication alone may not prevent recurrence.
Several factors increase susceptibility. People wearing occlusive work boots or persistently damp footwear may be particularly vulnerable. Diabetes, especially when blood glucose is poorly controlled, increases the risk of candidal skin infections. Immunosuppression, including that associated with systemic corticosteroids or chemotherapy, can also facilitate infection. Broad-spectrum antibiotics may contribute by disturbing the normal microbial balance. However, interdigital candidiasis can develop without an underlying systemic illness, and its presence should not automatically be interpreted as evidence of diabetes or immune deficiency.
The characteristic lesion is a moist, red, superficial erosion bordered by whitish, softened skin. The affected web space may appear raw or glazed, with peeling at its margins. Itching, burning, tenderness, and painful fissuring can occur, particularly when walking creates friction. Small peripheral papules or pustules may support a candidal diagnosis, although these are not always evident in narrow toe spaces. Appearance alone is insufficient for certainty because several infectious and inflammatory disorders produce similar interdigital changes. Mixed infections can further obscure the clinical picture.
The main diagnostic challenge is distinguishing candidiasis from interdigital tinea pedis, commonly called athlete’s foot. Tinea is caused by dermatophytes rather than Candida, but both can cause scaling, maceration, and fissuring. Other possibilities include irritant or allergic contact dermatitis, erythrasma, and bacterial toe-web infection. Marked malodour, discharge, or greenish discoloration should raise suspicion of bacterial involvement, including Pseudomonas. Psoriasis occasionally enters the differential diagnosis. Therefore, an apparent fungal infection that does not improve with appropriate treatment warrants reassessment rather than repeated empirical prescriptions.
Diagnosis combines clinical examination with laboratory testing when the presentation is uncertain, recurrent, or treatment-resistant. Microscopy of skin scrapings prepared with potassium hydroxide may demonstrate budding yeast and pseudohyphae. Fungal culture can help identify the organism, while bacterial sampling is useful when secondary infection is suspected. Importantly, recovering Candida does not necessarily establish that it is the primary cause: yeasts can colonise already damaged skin. Laboratory findings must therefore be interpreted alongside the lesion’s appearance, symptoms, and response to treatment. Biopsy is rarely necessary.
Management begins with correcting the local environment. Feet should be washed gently and dried carefully, particularly between the toes. Changing damp socks, choosing breathable footwear, and allowing shoes to dry between uses reduce retained moisture. Excessive sweating may require additional management. Heavy moisturisers should generally not be applied within already macerated web spaces because they can increase occlusion. Harsh antiseptics, aggressive rubbing, and attempts to peel away softened skin may worsen barrier damage. Practical advice should account for occupational footwear requirements and the person’s ability to perform foot care.
Topical antifungal treatment is usually sufficient for localised disease. An azole such as clotrimazole or miconazole is commonly used; nystatin is another option for confirmed candidiasis. Unlike azoles, nystatin does not treat dermatophyte infections, making diagnostic accuracy important. Treatment duration depends on the preparation and clinical response. Oral antifungals, such as fluconazole, may be considered for extensive or refractory disease under medical supervision. Drug interactions and contraindications require review. Potent corticosteroids or steroid-only treatment should be avoided because they can mask infection and encourage persistence.
Although usually superficial, interdigital erosions can provide an entry point for bacteria and contribute to cellulitis. Spreading redness, warmth, swelling, increasing pain, fever, or an open wound requires prompt clinical assessment, especially in people with diabetes, neuropathy, or poor circulation. Prognosis is generally good when both yeast overgrowth and moisture are addressed. However, evidence specifically concerning toe-web disease is limited, and much management draws on broader candidal intertrigo guidance. Ultimately, successful care depends on accurate diagnosis, appropriate antifungal therapy, and sustained protection of the interdigital skin barrier.
Prevention also involves recognising early recurrence. Regular inspection can identify renewed whitening, soreness, or cracking before erosions enlarge. People unable to see or reach their feet may benefit from assistance or podiatry review. Persistent episodes should prompt investigation of continuing moisture and contributing factors.
References
- Schlager E, et al. Erosio interdigitalis blastomycetica: A review of interdigital candidiasis. Dermatology Online Journal. 2018. PubMed.
- DermNet. Candidal intertrigo. Clinical guidance.