AR Cosmetology key terms

A 0-to-14 scale measuring how acidic or alkaline a water-based solution is, with 7 neutral; hair and skin products are formulated to work within specific ranges on this scale.

Describes a product formulated with a pH between roughly 4.5 and 5.5, matching the natural acidity of hair and skin so it avoids swelling the cuticle or disrupting the mantle.

The thin, slightly acidic film of sebum and sweat on the skin surface that helps repel bacteria and retain moisture; products and services are designed to avoid stripping it.

A solution with a pH above 7 that softens and swells the hair cuticle, allowing water and chemicals to penetrate; relaxers, depilatories, and many shampoos rely on this effect.

The outermost layer of the hair shaft, made of overlapping scale-like cells that protect inner layers; its condition controls shine, porosity, and resistance to chemical penetration.

The middle layer of the hair shaft, composed of elongated cells containing melanin and keratin; it gives hair strength, elasticity, and color and is the target of coloring and waving chemicals.

The innermost core of the hair shaft, a soft, sometimes absent central channel of cells; it contributes little to hair strength or appearance and is not the focus of most services.

The pigment produced in the hair cortex and skin that gives color; its type and amount determine natural hair color and how strongly hair responds to lightening products.

The brown-to-black pigment found in hair and skin; higher amounts produce darker natural levels, which generally require stronger lightening to change.

The red-to-yellow pigment found in hair and skin; it is the last pigment to be removed during lightening and is responsible for the warm tones that appear as hair lifts.

The hair's ability to absorb and hold moisture, determined by the tightness of the cuticle; low porosity resists penetration, high porosity absorbs quickly but loses moisture easily.

The hair's ability to stretch and return to its original length without breaking; it indicates internal strength and helps predict whether hair can withstand chemical services.

A strong chemical link between protein chains in the cortex that gives hair its shape and strength; permanent waves and relaxers work by breaking and then reforming these bonds.

The fibrous protein that makes up the bulk of hair, skin, and nails; its arrangement and condition determine strength, texture, and how hair and nails respond to treatments.

An oily substance produced by sebaceous glands in the skin that lubricates skin and hair and helps form the acid mantle; excess or lack of it affects scalp and skin condition.

A condition or circumstance that makes a service or product inadvisable for a client, such as open scalp lesions, certain medications, or a previous allergic reaction; it must be identified before service begins.

A small amount of product applied to skin and observed for a period before a full service, used to detect an allergic reaction to color, relaxer, or other chemicals.

An immune reaction to a substance that can cause redness, swelling, itching, or difficulty breathing; a known allergy to a product ingredient is a reason to avoid that product entirely.

The pre-service conversation in which the cosmetologist assesses hair or skin condition, reviews the client's history and goals, and agrees on a plan and expected outcome before beginning work.

The hands-on assessment of a client's hair and scalp before service, checking texture, density, porosity, elasticity, and scalp condition to choose safe products and techniques.

Dividing hair into controlled, evenly sized portions using clips and a comb before cutting, coloring, or styling, so each area is worked consistently and the result stays balanced.

The angle at which hair is held away from the head while cutting; it controls how much length is removed and whether the resulting shape builds weight or layers.

A cutting technique in which hair is elevated and cut to create stacked layers that build weight and volume at a specific area of the head.

A section of hair cut shorter than the length beneath it to remove weight and create movement; layers can be blended or disconnected depending on elevation and sectioning.

A cut made with zero elevation so all hair in a section falls to one consistent length, producing a solid, heavy perimeter line with minimal layering.

A hydrogen peroxide solution that, when mixed with hair color, opens the cuticle and develops the color; its volume strength determines the amount of lift or deposit.

Permanent or demi-permanent color that requires a developer to enter the cortex and form new color molecules; it provides longer-lasting results than temporary or semi-permanent color.

A product, usually highly alkaline, that straightens curly or textured hair by breaking disulfide bonds in the cortex and rearranging them into a straighter pattern.

A product applied after a relaxer or permanent wave to stop the chemical action, restore the hair's pH, and rebuild disulfide bonds in the new shape.

A two-step chemical service that uses a reducing agent to break disulfide bonds and a neutralizer to reform them, creating lasting curl or wave in the hair.

A professional skin treatment that cleanses, exfoliates, extracts, massages, and applies treatment products to improve skin condition and relaxation.

Visual and tactile assessment of a client's skin during consultation, noting skin type, oiliness, hydration, pore size, and any conditions that affect product or treatment choices.

The removal of comedones or congestion from pores, typically after softening the skin with steam; it must be done gently and only where the skin is not inflamed or broken.

A plugged pore containing sebum and dead skin cells; an open comedone is dark at the surface, while a closed comedone is covered by skin and appears as a small bump.

The removal of dead cells from the skin's surface by mechanical or chemical means, which smooths texture and helps treatment products absorb more effectively.

A service that shapes and cares for the natural fingernails, including filing, cuticle care, hand massage, and polish application, performed with sanitized implements.

A service that cleans, shapes, and cares for the toenails and feet, often including soaking, exfoliation, callus reduction, massage, and polish.

The visible hard covering of the fingertip or toe, made mostly of keratin; its appearance and condition reflect the health of the nail bed and surrounding tissue.

The layer of dead skin at the base of the nail plate that seals the area between nail and skin; it is softened and gently pushed, never cut, during a standard manicure.

A fungal infection of the nail that can cause thickening, discoloration, and separation of the nail plate; it is a contraindication for nail services and requires medical referral.

The process of destroying most pathogenic organisms on nonporous implements and surfaces using an EPA-registered hospital-grade disinfectant, following cleaning and before reuse.

The lowest level of infection control: cleaning and reducing the number of organisms on surfaces and tools by washing with soap and water or using a designated cleaner.

The complete destruction of all microbial life, including bacterial spores, usually achieved with an autoclave; it is the highest level of infection control.

The required response to blood or body fluid on skin or a surface: stop the service, wear gloves, clean the area, disinfect with an EPA-registered product, and dispose of contaminated materials properly.

The practice of treating all blood and body fluids as potentially infectious and using barriers such as gloves and disinfectants with every client, regardless of known health status.

A Safety Data Sheet supplied by the manufacturer that lists a product's hazards, safe handling, first-aid measures, and storage requirements; it must be kept accessible in the salon.

The legal requirement that employees be informed about hazardous chemicals in the workplace and trained to read Safety Data Sheets and labels before handling those products.

Reusable tools such as shears, combs, and nippers; porous or nonporous implements must be cleaned and then disinfected between clients according to infection-control rules.

A client's agreement to a service after being told what it involves, the possible risks, and expected results; documenting it protects both client and cosmetologist.

Maintaining accurate client cards and service records, including products used, formulas, patch test results, and dates, as required for safe follow-up and regulatory compliance.