Hair and Scalp Care
Analysis is the first skill
Before recommending a product, analyze texture (diameter), density (number of hairs per square inch), porosity (ability to absorb moisture), elasticity (ability to stretch and return), and growth pattern. Low porosity resists moisture and can build up; high porosity absorbs quickly and loses moisture just as fast; elasticity below normal warns you to avoid chemical services.
Shampoos and conditioners
Shampoos are surfactants; their pH should be near the hair's natural range (roughly 4.5–5.5) so the cuticle stays flat. Clarifying shampoos remove buildup but are drying; conditioning shampoos are gentler. Conditioners are surface (coat and smooth), penetrating (moisturize the cortex), or protein (temporarily fill damaged areas). Hard water leaves mineral deposits; soft water can make rinsing feel slippery.
Scalp conditions you must recognize but cannot diagnose
Dandruff/pityriasis, seborrheic dermatitis, tinea capitis (ringworm - contagious, refer), pediculosis (lice - refer), folliculitis, and alopecia areata (refer). Hair disorders include trichoptilosis (split ends), trichorrhexis nodosa (knotted breakage), monilethrix (beaded hair), and fragilitas crinium. Hirsuties is excess hair growth in a male pattern; hypertrichosis is excess growth generally.
The trap
Questions often bait you into "treating" a medical condition. A cosmetologist may recognize, cleanse, and refer - not diagnose or treat. Scalp massage is contraindicated over abrasions, infection, or a recent chemical burn.
Worked example
A client with flaking, red, itchy patches along the hairline sits down. You note the condition, do not massage or apply product, do not diagnose, and refer her to a physician before performing a service.