Seasonality of Hair Shedding in Healthy Women Complaining of Hair Loss

In a 6-year study involving 823 healthy women who reported hair loss, researchers discovered a seasonal pattern in hair shedding. The study, which excluded women with known hair loss diseases or on hair loss-inducing medications, utilized trichograms to find that the highest proportion of telogen hairs occurred in July, with a secondary peak in April, and the lowest in February. These findings, which did not vary significantly with age or year, support the idea that environmental factors like photoperiod may influence hair follicle cycles. This seasonal variation is important for the accurate assessment of hair loss treatments in clinical trials, as it could affect the interpretation of results, and for providing proper diagnoses and treatment plans for patients.