Hair & scalp
Hair loss is examined as a decision tree, and one branch changes everything: once follicular openings are gone, the loss is permanent, scarring alopecia turns a routine referral into an urgent one.
- 1Diffuse or focal?
- 2Scarring or non-scarring?
- 3What pattern?
- 4Any inflammation or scale?
- 5What does the shaft look like?
Androgenetic alopecia
Non-scarringPatterned: bitemporal recession and vertex thinning (male pattern), widened central part with a preserved frontal hairline (female-pattern hair loss).
- Gradual, over years
- Family history
- Miniaturised hairs, thick and thin shafts side by side
The concept: Androgen-driven follicular miniaturisation; the follicles shrink but survive, which is why treatment can work.
Alopecia areata
Non-scarringThirunavukkarasye-Raveendran · CC BY 4.0
One or more smooth, completely bald round patches with normal-looking scalp skin.
- Abrupt onset
- Exclamation-mark hairs at the margin, narrower at the scalp
- Nail pitting in a subset
- Follicular openings preserved
- Spectrum: beard-only patches (alopecia barbae), total scalp loss (alopecia totalis), or whole-body loss (alopecia universalis)
The concept: Autoimmune attack on the hair bulb. The follicle is intact, so regrowth is possible, often with initially white hairs.
Telogen effluvium
Diffuse shedding across the whole scalp, more hair in the brush and drain, no bald patches.
- A trigger 2–4 months earlier: illness, surgery, childbirth, crash diet, new drug
- Positive gentle hair pull with telogen (club) bulbs
- Scalp looks normal
The concept: A stressor synchronises follicles into the shedding phase. Self-limited once the trigger has passed, the history carries the diagnosis.
Tinea capitis
Non-scarringPatchy hair loss with scale, broken hairs ('black dots'), typically in children.
- Scaly patch that looks like 'dandruff in one spot'
- Occipital lymphadenopathy, a strong clue in a child
- May boggy-swell into a kerion
The concept: Dermatophyte infection of the hair shaft, needs ORAL antifungals; topical cannot reach inside the shaft.
Traction alopecia
Non-scarringHair loss along lines of chronic tension, frontal and temporal margins with tight styling.
- Marginal thinning with retained 'fringe' of finer hairs
- History of sustained tension styles
- Early: perifollicular papules; late: permanent loss
The concept: Mechanical, and reversible early, but chronic traction scars the follicle. Early recognition changes the outcome.
Scarring (cicatricial) alopecia
ScarringPatches where the follicular openings themselves have vanished, smooth, shiny scalp.
- Loss of follicular openings on close inspection or dermoscopy
- Perifollicular redness or scale at active margins
- Itch, burn, or tenderness
- The named diseases: lichen planopilaris (and its frontal fibrosing form), folliculitis decalvans with tufted hairs and pustules, and central centrifugal cicatricial alopecia expanding from the vertex
The concept: The follicle is being destroyed and replaced by fibrosis, irreversible where established. Loss of follicular openings converts a routine referral into an urgent one, because only early treatment preserves what remains.