OR Cosmetology cheat sheet

Hair is composed mainly of keratin; the cortex (about 80-90% of fiber mass) holds melanin and determines strength, elasticity, and curl pattern, while the cuticle is the outer protective scale layer.

The hair growth cycle: anagen (active growth, roughly 2-7 years on the scalp), catagen (transition, about 2-3 weeks), and telogen (resting/shedding, about 3 months); roughly 10% of scalp hairs are in telogen at any time.

pH scale: hair and skin sit near pH 4.5-5.5; the acid mantle protects the cuticle. Alkaline products swell the cuticle; acidic products (pH 3.0-4.5) contract and smooth it.

Permanent wave chemistry: reducing agent (ammonium thioglycolate, pH about 9.0-9.5) breaks disulfide bonds; thio-free waves use cysteamine (pH about 6.5-7.0); neutralizer (hydrogen peroxide or sodium bromate) rebuilds bonds into the new shape.

Sodium hydroxide (lye) relaxers and guanidine hydroxide (no-lye) relaxers both convert hair to a straight configuration; both are strongly alkaline and require base and scalp protection with thorough neutralizing shampooing.

Oxidative (permanent) hair color: ammonia or another alkalizer opens the cuticle, peroxide developer lifts natural melanin and oxidizes dye intermediates inside the cortex into larger colored molecules.

Developer volume maps to peroxide strength: 10 vol = 3% (deposit only), 20 vol = 6% (1-2 levels lift), 30 vol = 9% (2-3 levels), 40 vol = 12% (3-4 levels, highest normally used on scalp).

Strand test, patch test, and elasticity/porosity assessment are standard pre-service checks; overlapping relaxer or lightener on previously processed hair risks breakage and chemical burn.

Sanitation hierarchy: clean with soap/detergent, sanitize with an EPA-registered hospital disinfectant on hard nonporous implements, and sterilize only with an autoclave or approved method; porous items that contact blood cannot be disinfected and must be discarded.

EPA-registered disinfectant must be mixed and used per label contact time (commonly 10 minutes) and changed at least daily or when visibly soiled; implements must be fully immersed.

Blood exposure protocol: stop service, glove, clean the wound, apply antiseptic and bandage, disinfect all contaminated tools, and discard porous contaminated items in a sealed bag.

Facial and skin care: Fitzpatrick skin types I-VI estimate sun sensitivity; type I always burns, type VI rarely burns. Exfoliation depth and light-device settings are adjusted by type.

Massage contraindications include fever, acute inflammation, contagious skin conditions, recent fracture, and uncontrolled hypertension; effleurage, petrissage, tapotement, and friction are the four basic movements.

Nail structure: the nail plate sits on the nail bed; the matrix produces the plate; the eponychium (cuticle area) and hyponychium are living tissue and must not be cut deeply.

Electrical safety: a GFCI interrupts current on ground fault; equipment must be UL-listed, cords inspected for damage, and water kept away from outlets.

Anatomy relevant to services: the three layers of skin (epidermis, dermis, subcutaneous), the seven bones of the skull, and the facial nerve (cranial nerve VII) which controls facial expression.

Standard precautions assume all blood and body fluids are infectious; hand washing before and after each client and single-use gloves for chemical services remain the baseline.

Ingredient label reading: products list ingredients in descending order of concentration; the first five ingredients typically make up the bulk of the formula.

State licensing boards set scope of practice, sanitation rules, and continuing education hours; license renewal cycles vary by state and must be verified locally.

Client record cards should document services, products used, patch/strand test results, and any adverse reactions, retained per state rules.

Product cost per service = (product cost / total applications per container); retail markup commonly follows a keystone (2x) or 3x multiplier depending on the salon model.

Service pricing must cover product cost, labor time, overhead, and profit; a common target is labor at 40-50% of service price.

Informed consent and clear communication about chemical risks (burns, breakage, allergic reaction) reduce liability; never guarantee a color result that depends on prior chemical history.

Universal waste and chemical disposal: relaxers, lighteners, and solvents must be disposed of per local environmental rules, never poured down a drain if prohibited.

Retail success depends on recommending products matched to the client's hair type, porosity, and chemical history, with usage instructions for home care.

Fungal infections (tinea capitis, tinea barbae) are contagious and require medical referral; tools must be disinfected and porous items discarded.

Contagious conditions requiring service refusal include head lice (pediculosis), scabies, impetigo, and active herpes simplex lesions.

Noncontagious scalp conditions include dandruff (pityriasis), seborrheic dermatitis, and psoriasis; medicated shampoos may be recommended but not diagnosed.

Hair loss categories: alopecia areata (patchy autoimmune), androgenetic alopecia (patterned, hormonal/genetic), telogen effluvium (shedding after stress/illness), and traction alopecia (from tight styling).

Hair porosity: low porosity resists moisture and needs heat and lightweight products; high porosity absorbs quickly but loses moisture, needing protein and sealing.

Elasticity test: a wet strand stretched should return to length; if it breaks or stays stretched, the hair is damaged and chemical services should be avoided or minimized.

Density and texture are separate: density is hairs per square inch; texture is the diameter of an individual strand (fine, medium, coarse).