Seasonal hair loss is a temporary increase in hair shedding that occurs at specific times of the year. This common occurrence often leads to concern as individuals notice more strands on their brush or in the shower drain. It is not a permanent form of hair loss but a temporary, exaggerated phase of the scalp’s natural cycle tied to environmental cues.
The Biological Basis of Seasonal Hair Shedding
Hair growth is governed by the hair growth cycle, which consists of three main phases. The anagen phase is the active growth period, lasting several years. This is followed by the catagen phase, a short transitional stage where growth stops. Finally, the telogen phase is a resting period lasting around three months, after which the hair is shed to make way for a new hair shaft.
Normally, 85% to 90% of scalp hairs are in the active growth (anagen) phase, with 5% to 15% in the resting (telogen) phase. Seasonal shedding occurs because a higher proportion of hair follicles prematurely shifts from the growth phase into the resting phase simultaneously. This collective shift may be influenced by environmental factors, such as changes in daylight hours and temperature fluctuations.
The prevailing theory suggests that increased summer sunlight and UV exposure may prompt the scalp to push more hairs into the telogen phase. Since the telogen phase lasts approximately three months, hair that entered the resting phase in mid-summer will not shed until late summer or early fall. This biological delay explains the timing of the noticeable increase in hair fall. The shedding itself is the exogen phase, where the old hair is ejected by the emerging new anagen hair beneath it.
Expected Duration and Peak Shedding Periods
Seasonal hair shedding is a self-limiting process that resolves without medical intervention. The typical duration for this temporary increase in hair fall ranges from a few weeks to two or three months. Once affected follicles complete their resting phase and re-enter the active growth cycle, shedding gradually returns to the normal baseline rate of 50 to 100 hairs per day.
The most common time for increased shedding to peak is during the autumn months, typically spanning September through November. This autumn peak is a delayed result of the maximum number of follicles entering the resting (telogen) phase during the summer, particularly around July. Studies show that the proportion of telogen hairs is highest in the summer, leading to the subsequent fall shedding.
Some individuals also report a smaller peak in shedding during the spring, around April or May. During these peak times, daily hair loss can temporarily double or triple, with some people shedding up to 150 to 300 hairs a day. This temporary increase is a normal part of the hair’s natural growth cycle.
Distinguishing Seasonal Shedding from Chronic Hair Loss
While seasonal shedding is a temporary event, it is important to recognize when hair loss may indicate a more serious, chronic underlying issue. Seasonal shedding is characterized by a diffuse increase in hair fall across the entire scalp. It does not lead to visible thinning, bald patches, or a receding hairline, and hair density remains largely unchanged.
The duration of the shedding is a key differentiator; if excessive hair fall persists beyond three months, it warrants professional evaluation. Chronic hair loss conditions, such as Telogen Effluvium or Androgenetic Alopecia (pattern baldness), involve different mechanisms and lead to more significant, visible changes. Telogen Effluvium, often triggered by stress, illness, or nutritional deficiencies, causes a sudden increase in shedding that feels heavier than seasonal loss.
Warning Signs Requiring Professional Evaluation
Unlike seasonal loss, chronic Telogen Effluvium can be continuous or intermittent for long periods, sometimes years, and may be accompanied by noticeable thinning across the scalp. Hair loss that includes patchy areas, a clearly receding hairline, or simultaneous symptoms should be investigated by a healthcare provider or dermatologist. A proper assessment can determine if the shedding is a normal cycle shift or a medical condition requiring targeted intervention.