The body normally hosts a variety of microorganisms including bacteria and fungi. Some of these are useful to the body, some produce no harm or benefits, while others may cause harmful infections. Fungal infections are caused by microscopic organisms (fungi) that can live on the skin. They can live on the dead tissues of the hair, nails and outer skin layers. Fungal infections include mold-like fungi (dermatophytes, which cause tinea infections) and yeast-like fungi (such as candida).

Cutaneous candidiasis involves infection of the skin with candida. It may involve almost any skin surface on the body, but usually occurs in warm, moist, creased areas (such as armpits and groins). Cutaneous candidiasis is fairly common. Candida is the most common cause of diaper rash in infants, where it takes advantage of the warm moist conditions inside the diaper. The most common fungus to cause these infections is Candida albicans.

Candida infection is particularly common in individuals with diabetes and in people who are obese. Antibiotics and oral contraceptives increase the risk of cutaneous candidiasis. Candida can also cause infections of the nail, referred to as onychomycosis, and infections around the corners of the mouth, called angular cheilitis.

Oral thrush, a form of candida infection found on the mucous membranes of the mouth, may be a sign of HIV infection or other immunodeficiency disorders when it occurs in adults. Infected individuals are not usually considered infectious to others, though in some settings transmission to immunocompromised people can occur.

Candida is also the most frequent cause of vaginal yeast infections, which are extremely common.