The observation of animals shedding their coats during certain times of the year often leads to questions about whether humans experience a similar phenomenon. As seasons change, many individuals notice alterations in their hair’s behavior, prompting curiosity about seasonal hair loss.
The Seasonal Shedding Question
Studies have indicated that a higher proportion of human scalp hairs enter the resting (telogen) phase during the summer months. This often results in increased hair shedding approximately two to four months later, typically peaking in autumn and extending into early winter. A less pronounced increase in shedding can also occur in spring. This observed seasonal variation suggests that while humans do not “shed their coat” in the same way animals do, their hair growth cycle can be influenced by environmental shifts. The highest rates of hair shedding are commonly noted in late summer and autumn, while the lowest rates of resting hairs, and thus shedding, are often found in late winter.
Understanding Hair Growth Cycles
Hair growth follows a continuous cycle involving three main phases: anagen, catagen, and telogen. The anagen phase is the active growth period where hair follicles rapidly produce new hair cells. This phase can last anywhere from two to seven years, determining the potential length of one’s hair.
Following active growth, hair enters the catagen phase, a short transitional stage lasting only a few weeks. During this time, hair growth slows, and the hair follicle detaches from its blood supply. The final stage is the telogen phase, a resting period when the hair remains in the follicle but is not actively growing. About 10-15% of scalp hairs are in this phase at any given moment, which typically lasts around three months. Shedding is a normal part of this cycle, occurring as new hair growth pushes old hair out of the follicle.
Factors Influencing Winter Hair Changes
Several environmental and lifestyle factors prevalent in winter can influence hair health. Reduced sunlight exposure during winter months affects vitamin D levels, which are important for hair follicle health. Lower vitamin D can accelerate hair shedding. Additionally, decreased sunlight can lead to increased melatonin production, which some research suggests might influence hair cycles.
The dry air characteristic of winter, both outdoors and from indoor heating, can strip moisture from the scalp and hair. This dryness can lead to brittleness, frizz, and increased hair breakage. Temperature fluctuations, moving between cold outdoor and warm indoor environments, can also contribute to hair dryness.
Dietary habits also play a role, as winter diets may sometimes lack the variety of nutrients found in other seasons. Deficiencies in essential nutrients like protein, iron, zinc, and vitamins (C, D, E, biotin) can impact hair growth and contribute to shedding. Furthermore, stress, often heightened during the holiday season or due to seasonal affective disorder, can trigger a condition called telogen effluvium. This condition causes a significant number of hair follicles to prematurely enter the resting phase, leading to noticeable shedding a few months later.
When to Seek Professional Advice
While some seasonal hair shedding is a normal part of the hair growth cycle, certain signs indicate it may be time to consult a healthcare professional. If you experience sudden, excessive hair loss, or if you notice distinct patchy hair loss, it warrants medical attention. Other concerning signs include scalp symptoms such as persistent itching, redness, soreness, or the presence of flakes. If hair loss is accompanied by other bodily symptoms like unexplained fatigue or significant weight changes, these could point to broader health issues. Consulting a doctor or dermatologist is recommended if over-the-counter hair loss treatments have not yielded results after several months.