In both men and women the main cause of generalised hair loss is called androgenetic alopecia. In this condition, hormonal imbalance combined with hereditary predisposition produce thinning and pattern baldness. Less common causes include high fever, severe infection, diet, certain medications, birth control pills, thyroid disease, childbirth and cancer treatment. Male pattern baldness usually begins with a receding hairline and thinning at the crown and continues to progress over a lifetime. Female pattern baldness usually consists of thinning across the top of the scalp with preservation of the frontal hairline. Although the ultimate degree of baldness cannot be accurately predicted, the age of onset and the family history are important factors. Localised hair loss occurs due to scars and localised infections. Hair loss & hair fall are two separate things. Hairfall is a natural daily occurrence. The human head contains over 100,000 hairs and one normally sheds 100 to 150 hairs a day. Every hair is genetically programmed and follows a schedule that includes growth [anagen], resting[catagen] and shedding[telogen]phases. In general 85% of the hair on your head grow approximately 1 centimeter per month for about 2 to 6 years & then fall off. However, hair on back of your head are genetically programmed & scheduled to last long. People retain hair at the back of their heads even after 65 years of age. Baldness is often blamed on poor circulation to the scalp, vitamin deficiencies, dandruff, and even excessive hat-wearing. All of these theories have been disproved.