The average person sheds between 50 and 100 hairs each day as a natural part of the renewal process. Many people observe a distinct, temporary increase in hair loss during certain times of the year, known as seasonal shedding. This fluctuation is different from clinical hair loss conditions, which involve chronic loss and a failure of the hair to regrow. Understanding the hair growth cycle helps explain why these seasonal fluctuations occur.
Understanding the Hair Growth Cycle
Each hair follicle operates independently, cycling through three distinct phases across its lifespan. The longest stage is the Anagen phase, a period of active growth that typically lasts between two and seven years, encompassing about 85 to 90 percent of the hairs on the scalp.
Following this prolonged growth, the hair enters the Catagen phase, a short transitional period of two to three weeks where growth stops and the hair follicle shrinks. This phase marks the end of active hair production.
The final stage is the Telogen phase, a resting period that lasts approximately two to four months. Seasonal variations are rooted in the synchronization of this Telogen phase, where a larger percentage of follicles enter the resting state simultaneously. When the Telogen phase concludes, all those synchronized hairs are shed, making way for new growth to begin.
Peak Periods for Seasonal Hair Shedding
The most significant hair fall occurs in late Summer and early Autumn, often peaking around September or October. This increased shedding is a delayed reaction, reflecting a trigger that occurred two to four months earlier, which is the typical duration of the Telogen phase. Studies support this observation, showing a peak in resting hairs during the late Summer months.
A less pronounced, secondary peak in shedding is sometimes observed during the Spring months, generally between March and May. This timing suggests a seasonal rhythm where the body adjusts the hair growth cycle twice a year in response to environmental shifts. The increased shedding is usually temporary, lasting for about four to eight weeks before the hair growth rate returns to normal.
Biological Triggers of Seasonal Hair Changes
The increased synchronization of the hair cycle is thought to be an ancient biological adaptation. One theory suggests humans evolved to retain a denser coat of hair during the summer months to protect the scalp from intense ultraviolet (UV) radiation and heat. This protective hair is then shed once the summer ends.
Environmental factors like increased UV exposure during summer can directly trigger more follicles to prematurely enter the Telogen phase. Decreasing hours of daylight as summer transitions to fall can also influence hormonal balance.
Changes in hormones like Melatonin and Prolactin, which vary with light exposure, are known to affect the hair cycle. This hormonal shift pushes a greater number of hairs into the resting state, leading to the noticeable increase in shedding several months later.
When to Seek Professional Advice
While seasonal shedding is a normal, temporary process, it must be distinguished from chronic hair loss conditions. Consultation with a dermatologist is appropriate if the increased shedding persists for longer than six months or significantly exceeds 100 hairs per day. Visible thinning, particularly in areas like the crown or a receding hairline, may indicate a more serious condition like Androgenic Alopecia.
Other signs warranting medical attention include the sudden appearance of smooth, distinct bald patches, which may suggest an autoimmune condition. It is also important to seek professional advice if the hair loss is accompanied by symptoms such as an itchy, painful, or red scalp.
Supporting hair health during peak shedding involves gentle handling, such as avoiding excessive heat styling. Ensure a diet rich in nutrients like iron and zinc, which are necessary for healthy follicle function.