People do tend to experience seasonal hair loss, especially in the fall months of October and November. Two primary theories have been presented as to why this phenomenon occurs.
One theory for seasonal hair loss is that humans, like other animals, shed their hair in the fall in preparation for growing thicker hair for the winter ahead, explains Dr. Robert Leonard of Leonard Hair Transplant Associates. The other theory states that hair follicles are inflamed or damaged during the hottest months of summer, and three to four months later, the damaged hairs fall out, Leonard further notes. A Swedish study recorded higher rates of telogen, the resting phase hair goes through before falling out, in the month of July, possibly as a result of heat-related stress, according to The Belgravia Center.
While seasonal hair loss is normal, see a doctor if hair loss totals more than about 100 strands per day for prolonged periods, as this may indicate male or female pattern baldness or another underlying condition.