A fungal nail infection occurs from the overgrowth of fungi in, under, or on the nail. Fungi thrive in warm, moist environments, so this type of environment can cause them to naturally overpopulate. The same fungi that cause jock itch, athlete’s foot, and ringworm can cause nail infections.
Fungi that are already present in or on your body can cause nail infections. If you have come in contact with someone else who has a fungal infection, it may have spread to you. According to the American Academy of Dermatology (AAD), fungal infections affect toenails more commonly than fingernails because your toes are usually confined to your shoes, where they’re in a warm, moist environment.
If you get a manicure or pedicure at a nail salon, be sure to ask how the staff disinfects their tools and how often they do it. Tools, such as emery boards and nail clippers, can spread fungal infections from person-to-person if they’re not sanitized.