MD Cosmetology key terms

A 0-to-14 measure of acidity and alkalinity. Hair and skin are mildly acidic near 4.5 to 5.5; strong alkalis swell the cuticle and can cause damage.

The tough, overlapping outer layer of the hair shaft that shields the inner layers. Its condition controls shine, porosity, and how readily chemicals penetrate the hair.

The thick middle layer of the hair shaft containing keratin bundles and melanin. It gives hair strength, elasticity, and color, and it is where chemical coloring and waving act.

The innermost core of the hair shaft, made of loosely packed cells. It may be absent in fine or light-colored hair and has little effect on chemical services.

The ability of hair to absorb and hold moisture, determined by cuticle condition. Low porosity resists absorption; high porosity absorbs quickly but loses moisture and color fast.

The ability of wet hair to stretch and return to its original length. Normal hair stretches roughly half its length; poor elasticity signals damage and limits chemical services.

A shampoo formulated near the natural acidity of hair and scalp, often around pH 4.5 to 5.5. It helps close the cuticle, reduce tangling, and preserve color-treated hair.

An alkaline chemical used in many permanent hair colors and lighteners. It swells the cuticle and raises pH so dye intermediates and peroxide can enter the cortex.

A hydrogen peroxide solution mixed with permanent color or lightener. Its strength, usually labeled in volumes, controls the amount of lift and the deposit of color.

A small test service performed on a hidden section of hair before a chemical process. It predicts timing, result, and possible damage, and is required practice for lightening and relaxing.

A small application of a product such as hair dye or adhesive to the skin, usually behind the ear or in the elbow crease, checked after 24 to 48 hours for allergic reaction.

A highly alkaline cream or lotion, typically sodium hydroxide or guanidine hydroxide, that straightens curly hair by breaking disulfide bonds in the cortex. It requires careful scalp protection and timing.

A strong chemical link between cysteine amino acids in hair keratin. Permanent waving and relaxing break and re-form these bonds to change hair shape.

A two-step chemical service that uses a reducing agent to break disulfide bonds and a neutralizer to rebuild them around a rod, creating lasting curl.

The second solution in a permanent wave, usually a hydrogen peroxide or sodium bromate product. It rebuilds disulfide bonds in the new shape and stops the waving action.

Two application methods for hydroxide relaxers. Base relaxers use a protective cream on the scalp first; no-base formulas are applied directly and are more likely to irritate skin.

A six-level classification of skin type based on response to ultraviolet light and tendency to burn or tan. Estheticians use it to judge treatment risk and sun protection advice.

The outermost layer of the epidermis, made of flattened, keratin-filled cells. It is the skin barrier that exfoliants, cleansers, and topical products must act upon.

The outer, avascular layer of skin where new cells form and migrate outward. It contains melanocytes and provides the barrier against water loss and infection.

The pigment produced by melanocytes that gives skin, hair, and eyes their color and helps absorb ultraviolet radiation. Its amount and distribution determine Fitzpatrick skin type.

Removal of dead cells from the skin surface by mechanical scrubbing or chemical agents such as alpha hydroxy acids. Overuse damages the barrier and causes irritation or pigmentation problems.

Application of an acid solution to remove outer skin layers and improve texture or pigmentation. Depth and risk depend on the agent, concentration, skin type, and pretest results.

Darkening of skin after injury or inflammation, such as picking, waxing, or aggressive extractions. It is more common and persistent in darker skin types and requires gentle technique.

Water that evaporates through the skin barrier without sweating. High loss indicates a compromised barrier and calls for gentle cleansing, moisturizers, and reduced exfoliation.

A number comparing how long a sunscreen delays burning compared with unprotected skin. Higher values give more protection, and products must be reapplied after sweating or swimming.

Manual removal of blackheads and whiteheads using gentle pressure with fingers wrapped in tissue or a comedone extractor. It requires clean technique and is limited to non-inflamed lesions.

The visible hard keratin structure covering the nail bed. It protects the fingertip and is affected by filing, product application, and moisture balance.

The pink tissue beneath the nail plate, rich in blood vessels. Damage or separation from the plate creates a visible pocket where moisture and microorganisms can collect.

The portion of the nail plate extending beyond the fingertip. It is filed to shape the nail and is the area most prone to splitting and lifting of coatings.

The living skin at the base of the nail plate, commonly called the cuticle area. It seals the nail matrix from debris and should be softened and pushed back, never cut.

The tissue beneath the proximal nail fold where new nail cells form. Injury or infection here permanently alters nail growth and shape.

Separation of the nail plate from the nail bed, leaving a white or yellow gap. It can follow trauma, aggressive filing, or infection and is a contraindication for nail services.

Any disease, disorder, or deformity of the natural nail. A cosmetologist may not diagnose or treat it and should refer the client to a physician when it is suspected.

A number describing abrasive coarseness; lower numbers mean coarser files. Coarse grits remove product quickly but can thin the nail plate, so grit must match the task.

Destroying most pathogenic microorganisms on nonporous implements using an EPA-registered hospital disinfectant. Items must be cleaned first and immersed for the label contact time.

Destroying all microbial life, including spores, usually with an autoclave. It is required for items that penetrate skin or contact blood and is stronger than disinfection.

Reducing contamination on surfaces and tools by washing with soap and water and using low-level products. It is a routine first step, not a substitute for disinfection.

The safe response to bleeding: stop the service, wear gloves, clean the area, disinfect with an EPA-registered tuberculocidal product, and dispose of contaminated materials properly.

Treating all blood, body fluids, and non-intact skin as potentially infectious. Gloves, handwashing, and barrier protection are used with every client regardless of appearance.

The services and procedures a licensed professional is legally permitted to perform. Maryland licensees must stay within their license category and refer medical conditions to physicians.

The state regulatory body that licenses cosmetologists, estheticians, nail technicians, and salons, sets sanitation rules, and investigates complaints and violations.

Credits a Maryland licensee must complete to renew a license, including specified hours in health and safety topics. Proof must be kept and reported as the Board directs.

The periodic process of paying fees and showing required education to keep a Maryland license active. Working on an expired license is a violation subject to penalty.