The observation that hair seems to shed more heavily in spring is common. Normal daily hair shedding typically involves losing between 50 and 100 strands as part of the natural hair cycle, a rate that usually goes unnoticed. However, when many hair follicles move into the resting phase simultaneously, the subsequent synchronized shedding becomes far more noticeable. Studies have confirmed that the human hair cycle exhibits an annual periodicity. This temporary increase in hair fall, often observed in spring, reflects a biological adjustment to environmental changes.
Understanding the Hair Growth Cycle
Hair growth follows a cyclical pattern, ensuring continuous renewal, which occurs in three main phases: Anagen, Catagen, and Telogen. The Anagen phase is the active growth period, which can last anywhere from two to eight years, depending on genetics. At any given time, approximately 85% to 90% of a person’s hair is in this long-lasting growth phase.
The Catagen phase is a brief transitional stage that signals the end of active growth. This phase lasts only about two to three weeks, during which the hair follicle shrinks and detaches from its blood supply. Only a small fraction, around 1% to 5% of all hairs, are in this transition at once.
The Telogen phase is a resting period for the hair follicle, lasting about two to four months. The hair strand remains in the follicle during this time, but no growth occurs. At the end of the Telogen phase, the hair is released and shed, allowing the follicle to begin a new Anagen phase. Around 10% to 15% of all hair is typically in the Telogen phase at any point.
Scientific Basis for Seasonal Shedding
The increase in shedding observed in the spring is a delayed reaction to hairs entering the Telogen phase two to four months prior. Research suggests two common periods of increased hair shedding: one in the autumn and a less pronounced one in the spring (typically February to April). This temporary synchronization is a form of Telogen Effluvium, where more hairs than normal shift into the resting and shedding phases.
One prominent theory links the phenomenon to an evolutionary response, particularly regarding sunlight and temperature. Studies have shown that the proportion of hair in the Telogen phase is maximal in summer, which means the shedding occurs a few months later. It is hypothesized that the body may retain more hair during the warm summer months to protect the scalp from intense ultraviolet (UV) radiation.
Seasonal shifts in hormones, such as melatonin and prolactin, may also play a role in regulating the cycle. Melatonin, a hormone influenced by the length of daylight, acts directly on hair follicles and can affect the duration of the growth phase. Changes in daylight exposure and temperature throughout the year can subtly alter the balance of these hormones, nudging more follicles to prematurely enter the resting phase.
It is important to differentiate this normal, temporary seasonal shedding from chronic hair loss. Seasonal hair shedding is a temporary event, usually lasting about four to six weeks, after which the shedding rate returns to normal. If the increased hair fall is accompanied by noticeable thinning or persists beyond six weeks, it may indicate a more significant underlying issue like a nutritional deficiency or chronic Telogen Effluvium.
Supporting Hair Health During Seasonal Changes
A balanced diet rich in specific micronutrients is important during periods of increased seasonal shedding to promote quicker recovery and regrowth. These nutrients provide the necessary building blocks for strong hair and support the follicle’s function:
- Protein, which forms the structural basis of the hair shaft, must be consumed adequately through sources like eggs, lean meats, and legumes.
- Iron is necessary for proper hair growth.
- Vitamin C, found in citrus fruits, enhances iron absorption.
- Zinc supports follicle repair and development, and can be found in nuts and seeds.
Gentle handling practices minimize mechanical damage to strands already in the shedding phase. This involves using wide-toothed combs, avoiding excessive heat styling, and choosing mild, sulfate-free hair products. Maintaining a healthy scalp environment with regular cleansing helps ensure new hair can grow unhindered. If shedding appears excessive or lasts longer than six weeks, consulting a dermatologist is advisable.