ABSTRACT
Hair contributes significantly to the visual image of both males and females of all ages. Every visible major body surface is covered with some type of hair, providing the creation of endless opportunities for cosmetic adornment. Hair is nonliving, yet is immersed in a cycle of constant renewal and shedding. Unlike vital organs, such as the heart, liver, or kidneys, where limited cellular renewal can occur, hair growth occurs at the amazing rate of 0.35mm/day allowing the removal of old, damaged hair that is readily replaced with new regrowth.1 Hair is the only body structure that is completely renewable without scarring, as long as the follicle remains a functioning unit. For this reason, the hair can be subjected to insults that could not be sustained by any other body organ. This constant renewal also means that induced cosmetic alterations in shape, color, or texture are temporary until the chemically altered hair is sloughed or trimmed2 (Figure 1.1).
