ND Cosmetology cheat sheet

pH scale runs 0-14; 7 is neutral, below 7 acidic, above 7 alkaline. Hair and skin are naturally acidic (hair ~4.5-5.5, skin ~4.5-5.5).

The hair shaft has three layers: cuticle (outer protective scales), cortex (bulk, contains melanin and keratin), and medulla (central core, often absent in fine hair).

Keratin is the structural protein of hair, skin, and nails; it is held by disulfide, salt, hydrogen, and peptide bonds. Only disulfide bonds are broken by chemical texture/color services.

Melanin has two types: eumelanin (brown/black) and pheomelanin (red/yellow); hair color is determined by the ratio and density of each.

Nail plate composition: keratin, with sulfur cross-links; nail growth averages about 3.5 mm per month for fingernails and about 1 mm per month for toenails.

Bacteria are single-celled prokaryotes; viruses require a host cell to replicate; fungi are eukaryotic and include dermatophytes that cause tinea infections.

Standard precautions require treating all blood and body fluids as potentially infectious; handwashing with soap and water for at least 20 seconds remains the first-line control.

Disinfection destroys most pathogenic organisms on nonporous implements; sterilization destroys all microbial life including spores and is required for items that contact broken skin.

EPA-registered hospital-grade disinfectants must be used per label contact time; implements must be cleaned of debris before immersion because organic matter inactivates disinfectants.

Hair texture categories: fine, medium, and coarse. Porosity: low (cuticle tight, resistant), medium (normal), high (cuticle raised, absorbs and loses moisture quickly).

Density is the number of hairs per square inch; elasticity is the ability of wet hair to stretch and return - normal hair stretches about 50% of its length when wet.

Shampoo selection rule: low-pH, sulfate-free formulas for color-treated or dry hair; clarifying formulas only for buildup and not for daily use on chemically treated hair.

Cutting angles: 0 degrees = one-length blunt; 45 degrees = graduated; 90 degrees = uniform layers; 180 degrees = long-layered or shag.

Elevation determines where weight is distributed: lower elevation builds weight, higher elevation removes weight and creates movement.

A blunt cut creates a solid perimeter line; a razor cut creates soft, tapered ends because the razor slices the cuticle at an angle.

Cross-checking (cutting the opposite way) verifies balance and symmetry after the primary section is complete.

Texturizing shears remove 10-50% of hair volume depending on tooth spacing; they should not be used on the perimeter of fine hair.

Developer (hydrogen peroxide) volumes: 10 vol lifts 1 level, 20 vol lifts 2 levels, 30 vol lifts 3 levels, 40 vol lifts 4 levels; higher volumes also increase damage.

The law of color: primary colors are red, yellow, and blue; secondary colors are orange (red+yellow), green (blue+yellow), and violet (red+blue).

Neutralization rule: use the color opposite on the color wheel to cancel unwanted tone - blue cancels orange, violet cancels yellow, green cancels red.

Ammonia-free color uses ethanolamine or other alkalizers; it opens the cuticle less aggressively and generally lifts less than ammonia-based color.

Relaxer strength: no-lye (calcium hydroxide/guanidine) vs lye (sodium hydroxide); no-lye is gentler on the scalp but can leave more mineral buildup.

Relaxer processing rule: do not apply relaxer to previously relaxed hair except during a virgin relaxer retouch, and never overlap onto scalp already treated.

Thioglycolate is the active reducing agent in permanent waves; it breaks disulfide bonds, and the neutralizer (hydrogen peroxide or sodium bromate) rebuilds them.

Permanent wave test curl determines processing completion; check every 3-5 minutes until the desired S-pattern forms.

Strand test before any color or texture service verifies processing time, developer strength, and the result on that specific hair.

Skin types: normal, dry, oily, combination, and sensitive. Fitzpatrick scale I-VI classifies sun reactivity and guides treatment and product selection.

Skin analysis sequence: cleanse, magnifying lamp inspection, palpation for oiliness, and client consultation before any product application.

Facial massage movements: effleurage (gliding), petrissage (kneading), tapotement (tapping), and friction (rubbing); all are performed upward and outward.

Exfoliation types: mechanical (scrubs, brushes) and chemical (AHAs such as glycolic acid, BHAs such as salicylic acid). AHAs are water-soluble; BHAs are oil-soluble.

Contraindications for facial services include open lesions, sunburn, recent chemical peels, active cold sores, and known product allergies.

Extraction should follow softening with warm steam or compresses; do not extract inflamed cystic lesions - refer to a dermatologist.

SPF 30 or higher is the minimum recommendation for daily use; reapply every two hours with sun exposure.

High-frequency current is used for acne-prone skin and scalp treatment; it is contraindicated for clients with pacemakers or metal implants.

Nail structure: matrix (growth area), nail plate (body), nail bed, cuticle (eponychium), lunula (whitish half-moon), and hyponychium (seal under free edge).

Nail shapes: square, squoval, round, oval, and pointed; shape is chosen based on nail bed length and client lifestyle.

Pus, redness, swelling, and dark streaks under the nail are signs of infection and require referral to a physician; do not service.

Pedicure water temperature should not exceed about 100 degrees F (38 C); soak time is typically 5-10 minutes.

Metal pushers, nippers, and cuticle scissors must be cleaned, disinfected with an EPA-registered hospital disinfectant, and stored dry between clients.

Nail primer (methacrylic acid) improves adhesion for acrylics; it should not touch the skin because it can cause irritation.

Acrylic liquid is monomer (EMA) and powder is polymer; the ratio of liquid to powder controls cure time and strength.

Gel polish cures under UV/LED light; base coat, color, and top coat each need proper cure time or the service will lift.

Federal agencies affecting salons: OSHA (workplace safety, SDS access), FDA (cosmetics labeling, no pre-approval of cosmetics), EPA (disinfectant registration), and FTC (advertising).

State boards license cosmetologists and set sanitation, scope-of-practice, and continuing education rules; scope varies by state.

Material Safety Data Sheets (now Safety Data Sheets) must be accessible to all employees for every hazardous product in the salon.

OSHA Hazard Communication Standard requires labeling, SDS access, and employee training on hazardous chemicals.

Client records should be kept confidential and retained per state rule; release requires client written consent.

Scope of practice: cosmetologists may not diagnose or treat disease; suspected disorders must be referred to a physician.

Price and service terms must be disclosed before service; refund and cancellation policies should be in writing.

Independent contractor vs employee status affects tax withholding, insurance, and control over schedule; misclassification carries penalties.

Salon revenue formula: profit = total revenue minus (product cost + labor + rent + utilities + insurance + marketing).