The different kinds of hair loss

The hair follicle

We have approximately a hundred thousand hair follicles on our head, divided into 3 parts:
  • The hair bulb (the "root") , in the scalp
  • The epidermic shealth, the opening of the scalp's skin, that forms a canal allowing the hair stem to appear from the scalp
  • The hair stem composed of keratin

Each hair follicle has several hair cycles each composed of 3 phases
  • The anagene phase (an active phase of growing lasting from 3 to 7 years)
  • The catagene phase: a phase lasting for 1 to 2 weeks where growth stops, the root shrinks and results in death of the hair follicle
  • The telogene phase: the resting phase where the hair follicle remains attached to the scalp for 3 months before falling

The hair cycle consists therefore in a physiological loss of 50 to 100 hair follicles per day

Pathological loss

When the loss exceeds 60 to 100 follicles a day, it is considered to be pathological and further investigation may be necessary. It can result from disturbances of the various phases of the hair cycle:
  • Anagene phase: defect in the production of hair follicles because of hormonal and genetic factors (male and female pattern baldness), metabolic (iron deficiency, thyroid gland problems) and chemotherapy....
  • Telogene phase: telogene effluvium most common after pregnancy and severe illness, where considerable hair loss is shed. During pregnancy hair loss stops so after giving birth you loose the hair that you would have lost during that period. Hair loss (alopecia) is thought to be an auto immune disease, hair follicles can also present with structural anomalies of the stem or be destroyed by an infection such as ringworm (tinea), or trauma (burn) ...

The loss can generate some localised loss or balding patches, known as alopecia zones
We can distinguish two different alopecia types:
  • Scarring alopecia (the scalp is abnormal, scarred, hair follicles damaged and hair loss is permanent)
  • Non scarring alopecia (the scalp is normal in texture and appearance, hair follicles are not damaged and hair loss can resolve)

DR L.Rousseau
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