What causes hair to shed?

Goes thru cycle: Hair goes thru a cycle of anagen or growth and then telogen or death. 90% of hair on scalp is growing and 10% is dying.

Stress is number one: Normal hair loss is about 100 hair/day ... Stress, lack of adequate nutritional support, anemia, thyroid issues, dandruff are some additional common causes.

Hair shedding: Hair can shed for a number of reasons, such as iron deficiency, thyroid problems, medications, post-pregnancy, hormonal changes, severe stress, restrictive diets, an autoimmune condition called alopecia areata and a number of other reasons. Some people have seasonal shedding, which happens the same time each year and lasts a few weeks, then goes back to normal.