Hair loss refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scarring is not usually present. Hair loss in some people causes psychological distress. Common types include: male-pattern hair loss, female-pattern hair loss, alopecia areata, and a thinning of hair known as telogen effluvium.