Hair and Scalp Care, Shampooing, and Treatments
Structure and chemistry
Know the three layers: the cuticle (overlapping outer scales that control porosity), the cortex (the bulk, where color and curl chemistry happen), and the medulla (innermost, sometimes absent). Hair grows from the bulb of the follicle; sebaceous glands supply sebum. Hair and scalp prefer a mildly acidic pH, roughly 4.5 to 5.5, which is why alkaline products lift the cuticle and leave hair dull and rough.
A shampoo is a surfactant system: surfactant lifts oil and debris, water rinses it away, and conditioner - cationic, positively charged - smooths the negatively charged hair shaft. Recognize clarifying (buildup removal, not for daily use on dry hair), moisturizing/balancing, medicated (never a substitute for medical treatment), and waterless types. Treatments include rinse-through and deep conditioners, scalp treatments, and protein or moisture masks, always timed per the manufacturer.
Analyze before you prescribe: texture (fine to coarse), density (thin to thick), porosity (low, medium, high), elasticity (stretch and return), and scalp condition. High porosity takes and loses moisture and color quickly; low porosity resists both. Hair with poor elasticity snaps and is a poor candidate for chemicals.
Recognize but do not treat: alopecia, pityriasis (dandruff), tinea (ringworm, contagious), seborrheic dermatitis, pediculosis (lice), and folliculitis. Open sores, abrasions, sunburn, or a suspicious lesion mean no service and a referral.
Traps
- Vigorous scalp massage is wrong before a chemical service or on an inflamed scalp.
- Warm water to lather, cool to rinse; hot water strips and irritates.
- Density is not texture, and elasticity is not porosity.
Rule of thumb
Run the five-part analysis - texture, density, porosity, elasticity, scalp - before any chemical service. If elasticity fails, stop.