Candida is a type of yeast and is the most common cause of fungal infections. All healthy people generally have Candida yeasts on their skin, in their mouths and intestinal track. But it can become overgrown if the immune system is out of balance. In most cases, a candida fungal infection is usually an infection of the skin, fingernails, toenails or mucosal membranes and requires a moist environment for growth.