Fungi are a class of microorganisms that are found everywhere. Most do not cause any problems for humans, but some can live on the skin and be a cause of skin problems. Athletes foot, jock-itch, thickened nails and white patches on the skin are all caused by fungi. The symptoms of redness, itching, or small rings on the skin are the result of

your body’s response to the


USMLE Step 3 algorithms written and narrated by an expert in the field of USMLE test prep.