Hair & Skin Science — 10 Cosmetology Practice Questions

Hair growth begins in the hair follicle, specifically at the papilla — a small cone-shaped structure at the base of the follicle that contains the blood supply and nourishes the growing hair. The portion of hair below the skin is the root; the portion above the skin is the shaft. Damage to the papilla can affect or inhibit hair growth. Understanding the basic structures of the hair root (follicle, bulb, papilla) and the hair shaft is core hair science on the cosmetology exam.

The three main layers of the hair shaft are the cuticle (the tough, outermost protective layer of overlapping scales), the cortex (the middle layer that gives hair its strength, elasticity, and natural color through melanin), and the medulla (the innermost core, which may be absent in fine or very light hair). Most chemical services act on the cuticle and cortex. Knowing these three layers and their roles — especially that the cortex is where color and most chemical changes occur — is essential hair science.

The cortex is the middle layer of the hair shaft and contains the melanin (pigment) that gives hair its natural color, as well as providing most of the hair's strength and elasticity. Chemical services such as haircolor and perms work primarily within the cortex, which is why the cuticle must be opened to allow products to reach it. The cuticle is the protective outer layer, and the medulla is the innermost core. Understanding that natural color and chemical changes center on the cortex is frequently tested.

Pediculosis capitis is the technical term for an infestation of the scalp/hair with head lice. It is contagious and spreads through direct contact or shared items like combs, brushes, and hats. A cosmetologist who detects head lice should not perform the service and should refer the client appropriately, while ensuring tools and surfaces are properly cleaned and disinfected (or single-use items discarded). Recognizing common scalp conditions — and knowing which ones contraindicate service — is important hair-and-scalp science on the exam.

The epidermis is the outermost layer of the skin — the part you see and touch. Beneath it lies the dermis (the deeper, living layer containing blood vessels, nerves, glands, and hair follicles), and below that the subcutaneous (hypodermis) layer of fatty tissue. The epidermis itself has no blood vessels and is composed of several sub-layers, with the tough outer stratum corneum providing protection. Knowing the basic layers of the skin and their order is foundational anatomy for the cosmetology exam.

Sebaceous glands are the oil-producing glands of the skin; they secrete sebum, an oily substance that lubricates the skin and hair and helps form a protective barrier. The sudoriferous glands, by contrast, are the sweat glands, which help regulate body temperature and excrete some waste. Both are found in the dermis. Overactive sebaceous glands can contribute to oily skin and clogged pores. Knowing the two main types of skin glands and what they produce is part of basic skin science on the exam.

Primary functions of the skin include protection (acting as a barrier against the environment, microbes, and water loss), sensation (detecting touch, pressure, heat, cold, and pain through nerve endings), and heat regulation (controlling body temperature via blood flow and sweating), along with secretion of sebum, limited excretion, and limited absorption. The skin does not produce blood cells, digest food, or pump blood. Understanding the skin's core functions underpins safe and effective skincare services and is foundational exam content.

A cosmetologist who notices a suspicious or abnormal skin lesion — for example, a mole that is changing in size, shape, or color — should refer the client to a physician, because diagnosing and treating skin conditions is outside the cosmetologist's legal scope of practice. Cosmetologists are trained to recognize that something looks unusual and to refer, not to diagnose or treat. Performing services over suspicious lesions or attempting to treat them is inappropriate and potentially harmful. Knowing the limits of scope and when to refer is essential.

A cosmetologist should not perform a service when the client has an infectious, inflamed, or broken-skin condition of the scalp or skin — such as an active fungal infection (like ringworm), severe inflammation, open sores, or signs of infestation — because the service could spread infection or worsen the condition. In such cases, the client should be referred to a physician. Recognizing contraindications protects the client, the professional, and other clients. Distinguishing normal conditions from those that prohibit service is a key exam and safety skill.

Trichology is the technical term for the scientific study of hair and its diseases and care. (Dermatology is the study of skin, onychology is the study of nails, and histology is the study of tissues.) Cosmetologists apply trichology when analyzing a client's hair type, condition, and any scalp issues before a service. Knowing the correct '-ology' terms for hair, skin, and nails — trichology, dermatology, and onychology respectively — is commonly tested in the scientific-concepts section.