Hair and Scalp Anatomy, Disorders, and Scalp Care
Hair structure and growth
Hair is keratinized protein produced by the follicle. The shaft has three layers: cuticle (outer protective scales), cortex (main fiber mass with pigment), and medulla (central core, often absent in fine hair). The follicle is fed by the dermal papilla and attached to a sebaceous gland and arrector pili muscle. Vellus hair is fine and short; terminal hair is longer, thicker, and pigmented. Growth cycles are anagen (active growth, years), catagen (transition, weeks), and telogen (resting and shedding, about three months). Shedding 50–100 hairs daily is generally normal.
Scalp conditions you may see
Dandruff (pityriasis) is flaking without active infection. Seborrheic dermatitis causes oily scaling and redness. Tinea capitis is a fungal infection with scaling, broken hairs, and circular patches; it is contagious and requires medical referral. Pediculosis is head lice, also contagious. Alopecia areata produces smooth, round patches and is autoimmune, not contagious. Folliculitis shows pustules around follicles. Barber scope is observation, safe scalp care, and referral-not diagnosis or treatment.
Worked example
A client has round bald patches with broken hairs and scaly edges. The barber should not treat this as ordinary dandruff or proceed with a normal haircut using shared tools without infection-control precautions. The correct action is to stop, avoid sharing tools, and refer the client to a physician because tinea capitis is contagious. The shop then cleans and disinfects any potentially exposed nonporous tools.
Traps
Calling every flaky scalp “dry scalp” misses contagious fungal disease. Massaging or applying products to an infected area can spread infection. Do not promise regrowth for alopecia areata or sell treatment for a medical condition.