Many people notice increased hair shedding in late summer and early autumn months, an observation confirmed by dermatological science. This phenomenon is a documented biological pattern linked to the annual cycle of hair follicles. Understanding this temporary shift requires a look at the natural life cycle of individual hair strands.
Understanding the Hair Growth Cycle
Each hair follicle on the scalp operates on its own schedule, cycling through three primary phases of growth and rest. The first and longest phase is Anagen, the active growth stage, which typically lasts between two and seven years. During the Anagen phase, hair cells divide rapidly, forming the hair shaft.
Following active growth is the Catagen phase, a short transitional period lasting a few weeks. In this brief stage, the hair follicle shrinks, and growth ceases. The final phase is Telogen, which is a resting phase that lasts for approximately two to four months.
The Telogen phase is when the old hair is released and shed, allowing the follicle to remain dormant before the cycle restarts with a new Anagen hair. At any given time, approximately 85% to 90% of hairs are in the active growth phase, while the remaining 10% to 15% are in the resting or shedding phases. This asynchronous timing ensures that a person does not shed all their hair at once.
The Biological Reason for Autumn Shedding
The increase in hair loss experienced during the fall is scientifically referred to as seasonal Telogen Effluvium. This is a temporary condition where a higher-than-normal percentage of hairs enter the resting phase simultaneously. The biological trigger for this shift is thought to be an evolutionary response to environmental changes, particularly the increased sunlight and heat of the summer months.
Research suggests that the body’s protective mechanisms prompt a higher number of hair follicles to enter the Telogen phase during the summer. This may have been an adaptation to provide a denser hair coat for protection against intense ultraviolet (UV) radiation. The hair is not shed immediately when it enters this resting state.
There is a time lag between the environmental stimulus and the actual shedding event. Since the Telogen phase lasts around two to three months, hairs that entered this resting state in July or August are typically released from the scalp in October or November. This delay explains why the increased shedding is observed precisely when the seasons transition into autumn. The hair density returns to normal levels once the excess resting hairs have been shed.
When to Consult a Professional
While seasonal shedding is a temporary biological event, it is important to distinguish it from chronic or pathological hair loss conditions. Normal seasonal shedding is characterized by a general increase in loose hairs, but it does not lead to noticeable patches of baldness or a receding hairline. The increased loss should also be brief, typically resolving itself within six to eight weeks.
If the excessive hair fall continues for longer than two months, or if the amount of hair being shed seems higher than usual, it may indicate a different underlying issue. Signs that warrant a consultation with a dermatologist include a sudden appearance of patchy hair loss, significant thinning localized to the crown or temples, or visible inflammation or scaling of the scalp. These symptoms suggest the possibility of conditions like alopecia areata, androgenic alopecia, or chronic stress-induced effluvium, which requires medical evaluation.
Additionally, if the hair loss is accompanied by other symptoms, such as fatigue, unexplained weight changes, or changes in skin texture, a medical professional can investigate hormonal or nutritional deficiencies. A dermatologist can perform a physical examination and may order blood tests to rule out factors like thyroid dysfunction or anemia. Seeking early diagnosis ensures that non-seasonal hair loss is addressed with appropriate treatment.