Candidiasis is an infection caused by a group of microscopic fungi or yeast. There are more than 20 species of Candida, the most common being Candida albicans. These fungi live on all surfaces of our bodies. Under certain conditions, they can become so numerous they cause infections, particularly in warm and moist areas. Examples of such infections are vaginal yeast infections, thrush, skin and diaper rash, and nailbed infections.