Medical Encyclopaedia › Alopecia (short definition)
In brief: Losing up to about 100 hairs a day is normal. Hair loss (alopecia) is present when significantly more hairs fall out or the hair becomes visibly thinner. The most common form is hereditary hair loss.
Hereditary hair loss
In androgenetic alopecia, the hair follicles are sensitive to male hormones and become smaller over time. In men, this shows as a receding hairline and thinning at the crown; in women, as thinning in the parting area, usually with the hairline preserved.
Other forms
In alopecia areata, the immune system attacks the hair roots, creating round, bald patches. Diffuse hair loss can occur two to three months after fever, surgery, childbirth, major weight loss or stress, as well as with iron deficiency, thyroid diseases and due to medicines. Scarring forms, in which the hair follicles are permanently destroyed, require prompt dermatological treatment.
Diagnosis
The dermatologist examines the scalp with a dermatoscope (trichoscopy) and, if necessary, takes a trichogram. Laboratory tests such as ferritin, thyroid values and, in women, hormone levels help to find causes.
Treatment
For hereditary hair loss, minoxidil as a solution or foam is approved for men and women; in men, finasteride may also be considered. Both only work with continuous use. In alopecia areata, corticosteroids and, in severe forms, JAK inhibitors are among the treatments used. In diffuse hair loss, the focus is on treating the cause. A hair transplant is possible in stable hereditary hair loss. Many over-the-counter hair growth products and food supplements lack convincing evidence of effectiveness unless there is a deficiency.
When to see a doctor?
Sudden, severe or patchy hair loss, itching, redness or pain of the scalp, and hair loss with other symptoms should be assessed by a dermatologist.
Related terms in the encyclopaedia
Hair follicle, Alopecia areata, Minoxidil, Finasteride, Hair transplant, Iron deficiency, Hypothyroidism, JAK inhibitors, PRP treatment
Sources
- European Dermatology Forum (EDF): Leitlinie zur Behandlung der androgenetischen Alopezie bei Frauen und Männern
- Deutsche Dermatologische Gesellschaft (DDG): Patienteninformationen, derma.de
- IQWiG: gesundheitsinformation.de – Gesundheitsinformationen des Instituts für Qualität und Wirtschaftlichkeit im Gesundheitswesen
Note: This article is for general information and does not replace advice, diagnosis or treatment from a doctor or pharmacist. Last updated: October 2026.