A fungal infection that affects the fingernails or toenails is called onychomycosis. It is more prevalent on toenails. This is due to the environment inside the shoes. The fungus often spreads fast in environments that are warm and moist.
Fungal infections are commonly caused by a group of fungi known as dermatophytes. These microorganisms also cause ringworm, jock itch, and athlete’s foot. Yeasts and molds may also cause fungal infections.