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There are many types of
hair loss. It is often categorized according to when
it takes place during the hair growth cycle: anagen, catagen, and telogen.
Androgenetic alopecia is inherited hair loss. In this
type of hair loss, the growth (anagen) cycle becomes shorter and shorter. The
hair follicles sprout hairs that are thinner than normal. The hairs become
thinner and thinner, and eventually the follicles wither away.
Alopecia areata is a type of hair loss that is caused
immune system mistakenly attacks hair follicles. This
type of hair loss begins to get worse when hair follicles enter the rest
(telogen) phase too soon.
Telogen effluvium has many causes. In this type of hair loss, large
numbers of hairs enter the resting phase (telogen), which causes shedding and
thinning. Usually no more than 50% of the hair is affected, and hair loss may
occur up to 3 months after the event that causes it.1
Two types of hair loss not related to the hair growth cycle are
trichotillomania and traction alopecia.
Habif TP (2010). Hair diseases. In Clinical Dermatology: A Color Guide to Diagnosis and Therapy, 5th ed., pp. 913–935. Edinburgh: Mosby Elsevier.
Current as of:
March 12, 2014
Adam Husney, MD - Family Medicine & E. Gregory Thompson, MD - Internal Medicine
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