Graying of hairs has been suggested to be due to poor sustenance of melanocyte stem cells. With progressing age there is reduced melanocyte activity resulting in graying of hair. The beard and moustache hair may be affected earlier. The wave of graying progresses from the temporal to the vertical area and finally culminates in the occipital area. All the shades of gray and white can be observed from hair to hair as well as along an individual hair. Premature graying of hair may occur as an isolated autosomal dominant trait that begins before the age of 20. It may be associated with certain autoimmune diseases such as pernicious anemia, hyperthyroidism, and hypothyroidism. Several drugs like chloroquine, triparanol, fluorbutyrophenone, mephenesin, dixyrazine, and HIV infection may also cause premature graying of hair.