Seasonality of Hair Shedding


Is there a particular time of the year when hair shedding occurs more often?


Hair loss as a result of telogen effluvium occurs most commonly in autumn, with a second smaller peak occurring in the summer.


Telogen effluvium, an increase in the percentage of hair follicles in the telogen (resting) phase followed by subsequent increased hair shedding with new growth (anagen phase), is a common cause of perceived hair loss. Investigators identified 823 otherwise healthy women complaining to their clinician of hair loss between September 2001 and August 2007. Exclusion criteria included no history of alopecia or systemic disease, abnormal laboratory investigation, or use of drugs known to cause hair loss. Eligible women underwent telogen rate assessment using the trichogram technique, consisting of sampling at least 50 hairs (pulled out by their roots — ouch!) from the frontal and occipital scalp. A single investigator quantified different hair roots on the basis of their morphologic hair cycle characteristics. Telogen rates were statistically analyzed in relation to seasonal fluctuations. Telogen rates did not significantly relate to patient age, but the maximal proportion of telogen hair occurred in July. A second, less pronounced peak, occurred in April. Since the telogen phase duration is approximately 100 days, the authors estimate that maximal hair shedding would occur in October and November, with moderate hair shedding in June and July.


A number of otherwise healthy women with or without clinical alopecia complain of recurrent hair loss, presumably reflecting seasonality in the growth and shedding of hair. Objective: To test the hypothesis that periodicity in hair shedding reflects seasonal changes in human hair growth.


Methods: Retrospective case study over a period of six years of apparently healthy women with the complaint of hair loss. All underwent biochemical investigations, and trichograms were made.


Results: After exclusion of patients with a disease or on drugs known to cause hair loss, 823 women remained. Analysis of trichograms demonstrated annual periodicity in the growth and shedding of hair, manifested by a maximal proportion of telogen hairs in summer. A second peak seems to exist, though it is less pronounced, in spring. The telogen rates were lowest in late winter.


Conclusions: These results confirm the findings of former authors who have indicated seasonal changes in human hair growth, though this is the first study performed systematically in a representative number of women.


Copyright © 2009 S. Karger AG, Basel

Michael Kunza, Burkhardt Seifertb, Ralph M. Trüeba
Department of Dermatology, University Hospital of Zürich, and Biostatistics Unit, Institute for Social and Preventive Medicine, University of Zürich, Zürich, Switzerland
Dermatology 2009;219:105-110 (DOI: 10.1159/000216832)

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