title: Biology of the hair follicle and mechanisms of nonscarring and scarring alopecia.
abstract: There are many hair disorders, all of which involve alterations in normal hair biology. Essentially, hair disorders involve changes to hair fiber caliber, density per unit area, and/or the duration of anagen and telogen in the hair growth cycle. Hair disorders may be triggered by inflammation, genetics, the environment, or hormones; the relative contributions of these factors vary for different hair disorder diagnoses. Suitable treatments may either address the underlying causal factors or directly act on hair follicle biology. The objectives are to normalize the hair growth cycle, modulate the size of hair follicles, and potentially regenerate hair follicles to stabilize hair density. The purpose of this manuscript is to review the basic biology of the hair follicle, as well as causal mechanisms for the disordered hair follicle using some selected examples of hair disorders.
authors.affiliation: Department of Dermatology and Skin Science, The University of British Columbia, Vancouver, BC, Canada.|Department of Dermatology, Far Eastern Memorial Hospital, New Taipei, Taiwan.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Chu
authors.affiliation: Department of Dermatology and Skin Science, The University of British Columbia, Vancouver, BC, Canada.
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Santos
authors.affiliation: Department of Dermatology and Skin Science, The University of British Columbia, Vancouver, BC, Canada. kmcelwee@mail.ubc.ca.|Vancouver Coastal Health Research Institute, Vancouver, BC, Canada.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: McElwee
mesh_terms: D000505:Alopecia / Q000150:complications* / Q000209:etiology*; D002921:Cicatrix / Q000209:etiology*; D018859:Hair Follicle / Q000502:physiology*; D006801:Humans
keywords: environment; genes; hair disorders; hair loss; hormones; inflammation