title: Seasonality of hair shedding in healthy women complaining of hair loss.
abstract: BACKGROUND
  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 6 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.
authors.affiliation: Department of Dermatology, University Hospital of Zürich, Zürich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Kunz
authors.forename: Burkhardt
authors.initials: B
authors.lastname: Seifert
authors.forename: Ralph M
authors.initials: RM
authors.lastname: Trüeb
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000505:Alopecia / Q000175:diagnosis* / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D006197:Hair / Q000254:growth & development*; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D011336:Probability; D011379:Prognosis; D012189:Retrospective Studies; D012621:Seasons; D012720:Severity of Illness Index; D055815:Young Adult