Interdigital candidiasis: This is a common condition caused by a fungal infection, typically Candida, which thrives in warm, moist environments like the space between toes. The location and description of the rash make this a highly probable diagnosis.

Tinea pedis (athlete's foot): A fungal infection that can cause rash, itching, and cracking of the skin, often found between the toes.
Eczema (dyshidrotic eczema): Characterized by small, itchy blisters on the feet, including between the toes.
Contact dermatitis: An allergic reaction or irritation from substances like soap, detergent, or certain materials in shoes, which can cause a rash in the affected area.

Cellulitis: A bacterial skin infection that can cause redness, swelling, and warmth, potentially serious if not treated promptly.
Erythrasma: A bacterial infection that can cause a rash, typically in the intertriginous areas (skin folds), and is often mistaken for a fungal infection.
Squamous cell carcinoma: Although rare, any persistent or changing skin lesion should be evaluated for the possibility of skin cancer.

Pitted keratolysis: A bacterial infection that causes small pits in the skin, often accompanied by a foul odor, typically found on the soles of the feet but can occur between toes.
Keratoderma blennorrhagicum: Associated with reactive arthritis, this condition causes skin lesions on the feet, among other symptoms.
Granuloma glutiale infantum: A rare condition causing granulomatous lesions in the skin folds, including between the toes, typically in response to irritants or infections.