Hair Loss: Patterns, Causes and Assessment
Quick answer: Hair loss is a description, not one diagnosis. Gradual thinning, sudden shedding, patchy loss and scalp inflammation can have different causes. The pattern, timing, scalp findings, medicines and medical history help determine what assessment is appropriate.
Editorial disclosure: This page is an evidence-sourced summary of the cited American Academy of Dermatology patient resources. It has not been reviewed by a clinician and is not individual medical advice. It cannot diagnose a cause or determine what care is appropriate for you; seek advice from a qualified clinician for personal guidance.
Sources: American Academy of Dermatology overview, cause guide and diagnosis guide.
Patterns that can point to different causes
Hereditary pattern hair loss commonly appears as gradual thinning, a widening part, a receding hairline or a bald area. Other patterns include sudden shedding, patchy loss, loss related to repeated traction, and loss accompanied by inflamed or scaly scalp skin.
Sources: AAD overview and AAD cause guide.
An operation, major illness, high fever, childbirth, cancer treatment, some medicines, nutritional deficiency, thyroid disease, autoimmune disease, infection and tight hairstyles are among the factors that may be relevant. A temporal association does not by itself establish the cause.
Sources: AAD overview and AAD cause guide.
What a hair-loss assessment may include
Assessment commonly begins with questions about onset and speed, the distribution of loss, recent health events and medicines, followed by examination of the scalp, hair, nails and other affected areas. A gentle pull test may add information. Blood tests or a scalp biopsy are used selectively when the history and examination suggest they may help; they are not universal requirements for every person.
Sources: AAD overview, AAD cause guide and AAD diagnosis guide.
Why diagnosis comes before a treatment choice
No single hair-loss treatment fits every cause or every person. Some types may regrow without treatment, some may improve after a contributing factor changes, and others may need treatment to prevent further loss. Treatment choice should follow assessment of the cause.
Sources: AAD cause guide and AAD diagnosis guide.
Questions to take to an appointment
- Which features of my pattern and history are most useful for narrowing the cause?
- Could more than one cause be present?
- Would any test change the diagnosis or management, and why?
- What can the available evidence tell us, and what remains uncertain for me?
Source for HQ01: AAD diagnosis guide.
Source for HQ02: AAD diagnosis guide.
Source for HQ03: AAD diagnosis guide.
Source for HQ05: AAD diagnosis guide.
Information boundary
This page provides general education. It cannot diagnose an individual, determine candidacy, select a medicine or procedure, or predict an outcome. Individual assessment is needed for personal advice.
Clinical context: AAD overview and AAD diagnosis guide. The limits stated above are this publisher’s information-governance boundary.
Related research context only: source-by-source PRP evidence review. The linked page does not determine suitability or recommend a protocol.