Erosio interdigitalis blastomycetica (EIB) is a characteristic form of candidal infection that affects the skin between the toes and, less commonly, the fingers. In the feet, it is an important cause of painful, macerated interdigital lesions that can easily be mistaken for tinea pedis or simple “skin maceration”.
Definition and overview
EIB is an interdigital infection caused predominantly by Candida albicans, a yeast that normally colonises human skin and mucosa but becomes pathogenic in warm, moist, occluded environments. In the toes it typically presents in the web spaces, most often between the fourth and fifth toes, where friction and trapped moisture compromise the stratum corneum. The term itself reflects its pathology: “erosio” (erosion), “interdigitalis” (between digits), and “blastomycetica” (due to budding yeast), emphasizing the characteristic eroded lesion produced by a yeast infection. Clinically, it is viewed as a specific form of cutaneous candidiasis, sometimes grouped under interdigital candidiasis rather than as a distinct entity.
Epidemiology and risk factors
EIB can occur in any age group but is more frequently described in adults whose feet are chronically wet or occluded. People who wear tight, non‑breathable footwear for long hours (for example workers in rubber boots or closed safety boots) are particularly at risk, as the combination of sweating and poor ventilation provides ideal conditions for yeast proliferation. Systemic factors also matter: diabetes mellitus, obesity, peripheral oedema, and states of immune compromise all predispose to candidal skin infections, including EIB, by impairing local defence and promoting chronic moisture and skin breakdown. In addition, occupational or lifestyle habits that involve prolonged exposure to water or repeated washing, without adequate drying between the toes, increase the likelihood of disease.
Pathogenesis
The pathogenesis of EIB begins with damage to the interdigital stratum corneum from friction, moisture, and maceration. As the keratin barrier softens and breaks down, Candida albicans, already present as a commensal organism on the skin or introduced from other colonised sites, can invade the superficial epidermis. Yeast cells and pseudohyphae proliferate in the macerated keratin, triggering an inflammatory response that results in erythema, erosion, and further disruption of the barrier. The interdigital cleft, where opposing skin surfaces remain in close contact, maintains high humidity and warmth, sustaining the infection and hindering spontaneous resolution. Secondary bacterial colonisation, sometimes by Gram‑negative organisms, can complicate the picture and exacerbate odour, pain, and exudate, further enlarging the erosive lesion.
Clinical features in the feet
On the feet, Erosio interdigitalis blastomycetica most often affects one or more web spaces, classically presenting as an oval or fissured area of red, denuded skin surrounded by a rim of white, soggy, macerated epidermis. The lesion tends to look “raw” and moist, with surrounding whitish, peeling skin that may extend along the sides of adjacent toes. Patients typically complain of itching, burning, and tenderness, which can be aggravated by walking, standing, or wearing shoes. A foul odour is common when there is substantial maceration or bacterial co‑infection, and the area may crack or fissure, leading to sharp pain on weight bearing. In chronic or recurrent cases, the skin may show persistent scaling and intermittent erosions, and small vesicles or pustules may appear at the periphery, reflecting ongoing inflammation and superficial infection.
Differential diagnosis
Accurate diagnosis requires distinguishing Erosio interdigitalis blastomycetica from several other interdigital dermatoses of the feet. Tinea pedis, caused by dermatophytes, can also produce maceration and scaling between the toes, but often has drier, more powdery scaling and typically lacks the pronounced “raw” central erosion and odour associated with candidal infections. Interdigital erythrasma, due to Corynebacterium minutissimum, may present as macerated, reddish‑brown patches but characteristically fluoresces coral‑red under Wood’s lamp examination. Irritant or allergic contact dermatitis tends to show more diffuse erythema and scaling without the sharply demarcated, eroded centre, while soft corns (heloma molle) are painful focal hyperkeratoses rather than broad erosions. Bacterial intertrigo and simple soak maceration can resemble Erosio interdigitalis blastomycetica but often lack the pruritus, candidal pseudohyphae on microscopy, and classic white rim of macerated skin around a central erosion.
Diagnosis
Diagnosis is primarily clinical, based on the typical interdigital location and appearance of a macerated white rim surrounding an erythematous, eroded centre. However, because it mimics tinea pedis and other conditions, simple office investigations are important. Scraping from the affected web space can be examined in potassium hydroxide (KOH) preparation to look for budding yeast and pseudohyphae, confirming candidal involvement. Culture on appropriate media allows species identification and may reveal concomitant dermatophytes or bacteria, which can influence treatment choices. In atypical, resistant, or severe cases, a skin biopsy may be performed to rule out psoriasis, chronic eczema, or other dermatoses, and to demonstrate the presence of yeast organisms in the stratum corneum. Assessment of contributing systemic factors, such as hyperglycaemia in diabetics or oedema from venous disease, is also a key part of the diagnostic work‑up.
Management and treatment
Effective management of Erosio interdigitalis blastomycetica in the feet combines antifungal therapy with rigorous control of moisture and predisposing factors. Topical antifungals, such as azole creams or solutions (for example clotrimazole or miconazole), are usually first‑line and are applied to the affected web spaces and surrounding skin for several weeks, continuing briefly after apparent clinical resolution to reduce relapse. In situations with marked maceration, powders or solution formulations may be preferable to creams, as they help keep the area dry and reduce friction. If topical therapy fails, is poorly tolerated, or if the infection is extensive or recurrent, systemic antifungals such as fluconazole or itraconazole can be prescribed, taking into account liver function and potential drug interactions. Treatment should also target any secondary bacterial infection, using topical or systemic antibiotics when indicated.
Prevention and patient education
Prevention of recurrence is central, given the tendency of Erosio interdigitalis blastomycetica to reappear when moisture and occlusion persist. Patients are advised to wash feet daily with gentle cleansers and, most importantly, to dry thoroughly between each toe using a towel or even absorbent cotton or gauze. Choice of footwear is critical: breathable shoes made from materials that allow evaporation, combined with moisture‑wicking socks that are changed whenever damp, markedly reduce interdigital humidity. For individuals with occupational exposure to water or to prolonged boot wear, scheduled “dry‑out” breaks, use of antifungal or drying powders, and rotation of footwear can help maintain a drier environment. Addressing systemic risk factors, such as optimising glycaemic control in diabetes and managing oedema, further lowers susceptibility. Educating patients on early symptoms—itching, whitening of the web space, mild soreness—encourages prompt self‑care and early medical review, which can prevent progression to painful erosions and complications.