How does alopecia occur?
On the average scalp, there are about 100,000 hairs. Hair grows about one centimetre a month and lasts on the scalp for 3 to 5 years. It's normal to lose around 100 hairs from the scalp each day. If healthy new hairs continue to grow in place of those lost, no change in thickness is seen. Thinning and hair loss occurs when hair falls out rapidly, becomes damaged or doesn't grow back.