HI Cosmetology key terms

The process of significantly reducing the number of disease-causing germs on a surface or tool to a safe level, usually by cleaning with soap or detergent and water before any further disinfection step.

Destroying most harmful microorganisms on hard, nonporous implements using an EPA-registered hospital-grade disinfectant mixed and used according to label directions, typically after the tool has been cleaned.

The complete destruction of all microbial life, including bacterial spores, on an object. It requires an autoclave or approved sterilizing device and is not achieved by wiping tools with disinfectant.

A device that uses high-pressure steam to sterilize metal implements and porous items. Items must be cleaned and dried first, and the unit must be monitored for proper temperature, pressure, and time.

Disease-causing microorganisms such as hepatitis B, hepatitis C, and HIV that can be transmitted through contact with blood or other potentially infectious body fluids, making gloves and sharps precautions essential.

A standard approach in which every client is treated as potentially infectious, so gloves, handwashing, and barrier tools are used consistently regardless of appearance, known health status, or stated history.

Reusable tools such as shears, clippers, combs, and metal clips used during services. Classification as porous or nonporous determines whether cleaning plus disinfection or sterilization is required between clients.

A distinction based on whether a material absorbs liquids. Nonporous items like metal and glass can be disinfected; porous items such as towels, nail files, and wooden sticks cannot and must be discarded or replaced after use.

A Safety Data Sheet summarizes a product's hazards, safe handling, first aid, and disposal. Current practice uses the SDS format; sheets must be kept accessible for every chemical product in the salon.

The U.S. federal agency that enforces workplace safety rules, including hazard communication, bloodborne pathogen standards, and injury recordkeeping that apply to salon workplaces and employees.

The practice of storing, labeling, and handling salon chemicals so they cannot cause fire, inhalation injury, skin damage, or accidental mixing, including keeping products in original or clearly labeled containers.

Describes a product or agent that kills bacteria rather than merely stopping their growth. Disinfectant labels state which organisms the product is proven to kill, so the claim must match the label.

Describes an agent that destroys fungi, including the organisms that cause ringworm and athlete's foot. Salon disinfectants used on implements should carry a fungicidal claim on the label.

A product approved by the Environmental Protection Agency for killing specified germs on surfaces. The label lists contact time, dilution, and organisms killed, and those directions must be followed exactly.

A condition or circumstance that makes a service or product inadvisable because it could harm the client. Examples include open scalp lesions, certain allergies, or recent chemical burns, which require referral or service modification.

A small amount of product applied to a discreet area, such as behind the ear or inner elbow, and observed for 24 to 48 hours to detect an allergic reaction before a full service is performed.

The structured conversation before a service in which the practitioner reviews the client's history, hair or skin condition, goals, and any contraindications, then explains the plan and confirms consent to proceed.

A 0-to-14 scale measuring acidity and alkalinity, with 7 neutral. Hair and skin are mildly acidic near 4.5 to 5.5, and products outside that range can swell the cuticle or disrupt the skin barrier.

Describes a product formulated near the natural pH of hair and skin, roughly 4.5 to 5.5. Such products help close the cuticle, reduce swelling, and preserve color and moisture after chemical services.

Having a pH above 7. Alkaline solutions swell the hair cuticle and soften it, which allows lighteners and depilatories to act but also increases porosity and risk of damage if not controlled.

The layered anatomy of a hair strand: the outer cuticle, the middle cortex containing pigment and strength, and the central medulla. Each layer responds differently to chemicals, heat, and mechanical stress.

The tough, overlapping outer layer of the hair that protects inner structures and controls how much moisture and chemical enters. Rough or lifted cuticle makes hair feel porous and look dull.

The middle layer of the hair, made of elongated cells, that gives strength, elasticity, and most of the natural pigment. Chemical services act primarily here, so damage to it is largely irreversible.

The innermost, loosely packed core of a hair strand, sometimes absent in fine or light-colored hair. It contributes little to strength and is generally unaffected by normal salon chemical services.

The ability of hair to absorb and retain moisture, determined largely by cuticle condition. High porosity absorbs quickly but loses moisture fast; low porosity resists absorption and may need heat or longer processing.

The ability of wet hair to stretch and return to its original length without breaking. Good elasticity signals healthy protein bonds; poor elasticity warns that chemical or heat services risk breakage.

The repeating phases of hair growth: anagen, when hair actively grows; catagen, a short transition; and telogen, a resting phase before shedding. Understanding these helps explain shedding and treatment expectations.

A circular arrangement of primary, secondary, and tertiary colors used to predict color results. Opposites on the wheel neutralize each other, which guides toner and corrective color choices.

Colors positioned opposite each other on the color wheel, such as blue and orange or red and green. In hair color they neutralize unwanted tones, for example a blue toner on brassy orange highlights.

A hydrogen peroxide solution that, when mixed with color or lightener, opens the cuticle and supplies the oxygen needed to lift natural pigment and deposit artificial color. Volume strength controls the degree of lift.

A color product applied after lightening to adjust or neutralize the resulting tone and add shine. Toners are usually low-volume, deposit-only formulas and are not intended to lift natural pigment.

A method of isolating sections of hair in foil so lightener or color stays where placed and processes faster through retained heat. Placement and saturation determine the pattern and evenness of the result.

A strong alkaline cream, usually containing sodium hydroxide or a no-lye alternative, that breaks disulfide bonds to straighten curl. It requires careful strand testing, scalp protection, and strict timing.

A relaxing product based on ammonium thioglycolate rather than hydroxide. It works at a lower pH, is gentler on the scalp, and is often used for mild straightening or curl reduction rather than full relaxing.

A service that permanently alters curl by breaking and reforming disulfide bonds. Success depends on correct product strength, strand testing, thorough rinsing, and neutralizing to rebuild the bonds.

Cutting hair with a straight or guarded razor to create soft, textured ends and movement. It requires tension control and is usually avoided on very curly or fragile hair because it can cause frizz.

The angle at which hair is held relative to the head during cutting. It determines where length falls and how layers build, with 0 degrees producing a solid line and 90 degrees producing uniform layers.

A cut made with zero elevation so all hair falls to one length and forms a solid, heavy perimeter line. It requires precise sectioning and is the foundation for many graduated shapes.