The most common cause of hair loss is inheritance. Men and women inherit the gene for hair loss from either or both parents. Men are most commonly affected by the inherited gene as the hormone, testosterone, activates the genetic program causing loss of hair follicles. Currently there is no known method of stopping this type of hair loss. The age of onset, extent, and rate of hair loss vary from person to person. Severe illness, malnutrition, or vitamin deficiency can accelerate this process. When applied incorrectly, permanent hair color and chemical relaxers damage the hair and follicle to the extent that hair loss can be permanent. Causes of hair loss do not include wearing a hat, excessive shampooing, lack of blood flow, or clogged pores.