Topic Overview

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.

  • The anagen phase is when your hair grows-your
    hair follicle forms a new hair shaft. Most (90%) of the hair on your scalp is
    in a growing phase that lasts from 2 to 6 years.
  • The catagen phase
    follows the anagen stage. This is a 1- to 2-week transition stage between
    anagen and telogen. Less than 1% of your scalp hair is in this
    phase.
  • The telogen stage is the rest stage. At the end of this
    3- to 4-month phase, some of your hair falls out. Losing up
    to 100 hairs a day is normal. When a hair falls out, a new hair is grown in the
    same hair follicle, and the growing cycle begins again.

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
when the
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.footnote 1
Causes include:

  • Mental stress or physical stress, such as recent
    surgery, illness, or high fever.
  • Poor nutrition, especially lack of
    protein or iron in the diet.
  • Side effects of medicines, such as
    blood thinners (anticoagulants).
  • Changes in hormone
    levels, such as those that occur after childbirth, when taking birth control
    pills, or at menopause.

Two types of hair loss not related to the hair growth cycle are
trichotillomania and traction alopecia.

  • Trichotillomania is a compulsive behavior in
    which a person pulls hair out of the scalp, eyelashes, or eyebrows. There is
    usually mounting tension before pulling the hair and a feeling of relief
    afterward.
  • Traction alopecia involves hair loss around the edge of
    the hairline and is especially noticeable around the face and forehead. It is
    caused by your method of hairstyling. Certain hairstyles can pull hair too
    tight; for example, tight braids or tight ponytails can cause hair loss.

Related Information

References

Citations

  1. Habif TP (2010). Hair diseases. In Clinical Dermatology: A Color Guide to Diagnosis and Therapy, 5th ed., pp. 913-935. Edinburgh: Mosby Elsevier.

Credits

ByHealthwise Staff
Primary Medical Reviewer Adam Husney, MD – Family Medicine
Specialist Medical Reviewer Ellen K. Roh, MD – Dermatology

Current as ofOctober 5, 2017

Current as of:
October 5, 2017