Why Your Hair Is Shedding — And The Five Causes Derms See Most

Hair loss consultations are among the most emotionally loaded appointments in dermatology, and among the most treatable — provided the pattern is identified correctly, which requires looking at where the hair is thinning rather than only at how much is in the drain.

These are the five presentations dermatologists see most.

1. Telogen effluvium

Diffuse shedding across the whole scalp, typically starting eight to twelve weeks after a trigger: illness, surgery, a crash diet, childbirth, a bereavement, severe stress, or stopping hormonal contraception.

The delay is why people so often fail to connect it. It is self-limiting in most cases and regrows over six to nine months once the trigger has resolved.

2. Female pattern hair loss

Gradual widening of the central parting with preservation of the frontal hairline. Often familial, frequently accelerating around perimenopause.

It is progressive, so early treatment matters. Topical minoxidil is first line, with oral options available under specialist supervision.

3. Nutritional deficiency

Low ferritin is the classic driver in menstruating women. Vitamin D deficiency and inadequate protein intake also contribute, and severe caloric restriction reliably causes shedding.

“I check ferritin, thyroid function and vitamin D in essentially every hair consultation,” says Amira Haddad, MD. “A ferritin of 14 will not grow hair, whatever the lab's reference range says.”

4. Thyroid and hormonal causes

Both hypo- and hyperthyroidism cause hair loss, as can PCOS through androgen excess. The pattern in androgen excess is more concentrated at the crown and temples and often comes with other signs.

Postpartum shedding is a physiological telogen effluvium and resolves; it is worth saying so clearly because it frightens people badly.

5. Traction and scarring alopecia

Repeated tension from tight braids, weaves, extensions and very tight ponytails causes traction alopecia, initially reversible and eventually not.

Scarring alopecias, including frontal fibrosing alopecia and central centrifugal cicatricial alopecia, destroy the follicle permanently. “These need urgent specialist referral,” says Dr Kessler. “The window to preserve follicles is measured in months, and this is where delay causes irreversible harm.”