Written Exam Domain Review: Sciences, Chemistry, and Law

Why This Review Matters

The state barber licensing written examination tests knowledge you will use every day in the shop—protecting clients from infection, understanding how chemicals work on hair, and following the law that makes your license valid. Every domain on the exam connects directly to safe, legal, professional practice. Reviewing these domains systematically, and tracking where you are weakest, is the most efficient path to passing on your first attempt.

Domain 1: Bacteriology and Infection Control

Bacteria are single-celled microorganisms classified by shape: cocci (round), bacilli (rod-shaped), and spirilla (spiral). Cocci can appear in clusters (staphylococci), in chains (streptococci), or in pairs (diplococci). Most bacteria encountered in the barbershop are nonpathogenic (harmless) but some are pathogenic (disease-causing), which is why proper sanitation matters.

Key infection-control terms:

• Sanitation reduces the number of pathogens to a safe level on surfaces and tools.
• Disinfection destroys most pathogens (but not all spores) on nonporous surfaces; EPA-registered hospital-level disinfectants are required for implements that contact skin.
• Sterilization destroys all microbial life, including spores; autoclaves achieve this but are rarely required in barbershops under most state rules.

Safety point: Never place a used implement back into a disinfectant solution with a clean implement. Cross-contamination defeats the purpose of disinfection. Always use separate containers for soiled and disinfected tools.

Viruses, fungi, and parasites are also tested. Fungi cause conditions such as tinea capitis (ringworm of the scalp); this is a contraindication—do not perform services on an infected client. Refer the client to a physician.

Domain 2: Hair and Scalp Anatomy and Physiology

Hair is composed primarily of the protein keratin. The hair shaft has three layers: the cuticle (outermost, overlapping scales), the cortex (middle, contains melanin and gives hair its strength and color), and the medulla (innermost core, not always present). The follicle, sebaceous gland, arrector pili muscle, and blood and nerve supply make up the hair root structure.

The scalp has seven layers; the most clinically important are the skin, the subcutaneous layer, and the galea aponeurotica (epicranial aponeurosis). Knowing the structure of the follicle explains how chemical services penetrate and how damage occurs.

Safety point: Scalp abrasions, active infections, or open sores are contraindications to chemical services. Always conduct a scalp analysis before any chemical application.

Domain 3: Chemical Properties of Barbering Products

The pH scale runs from 0 to 14. A pH of 7.0 is neutral (pure water). Values below 7.0 are acidic; values above 7.0 are alkaline (basic). Hair has a natural pH of approximately 4.5–5.5. Understanding pH is essential for safe chemical services:

• Permanent wave solutions (thioglycolate-based) are alkaline; they raise the cuticle and break disulfide bonds so the hair can be reshaped.
• Neutralizers are acidic; they lower pH, close the cuticle, and reform disulfide bonds.
• Relaxers are strongly alkaline (sodium hydroxide relaxers can exceed pH 13); they permanently straighten hair by breaking disulfide bonds.
• Hydrogen peroxide (developer) is measured in volume; higher volume equals more oxidizing power and more lift.

Safety point: Always perform a strand test and skin/patch test before chemical services. Strong alkaline products can cause chemical burns if left on too long or applied to already-damaged hair or skin.

Domain 4: Electricity and Light Therapy Basics

Electricity used in barbering flows in two forms:

• Direct current (DC) flows in one direction; used in some electrology equipment.
• Alternating current (AC) reverses direction; the standard form from wall outlets.

High-frequency (Tesla) current is used in some scalp and facial treatments for its germicidal and stimulating effects. It produces a faint violet or orange glow depending on the electrode gas used.

Light therapy in the barbershop most commonly involves ultraviolet (UV) light (germicidal, used to sanitize tools in UV sanitizer cabinets—note these sanitize, not disinfect) and infrared light (heat, used to promote penetration of conditioning products).

Safety point: Never use electrical appliances near water. Inspect cords and plugs before each use. Clients with pacemakers or certain skin conditions may be contraindicated for electrical or light therapy treatments—always review health history.

Domain 5: State Barber Law and Professional Regulations

Your state barber law defines the legal framework for your license. Key concepts tested on the written exam include:

• Scope of practice: The specific services a licensed barber is legally permitted to perform as defined by state law.
• Licensing requirements: Minimum training hours, examination requirements, age, and educational prerequisites set by the state board.
• License renewal: Most states require periodic renewal and continuing education; practicing with an expired license is illegal.
• Salon/barbershop licensure: The establishment itself typically requires a separate license from the individual barber.
• Enforcement and penalties: State boards can issue fines, suspend, or revoke licenses for violations including practicing without a license, unsanitary conditions, or exceeding scope of practice.

Safety and legal point: Performing a service that falls outside your scope of practice—such as treating a medical condition—can result in license suspension and legal liability. When in doubt, refer the client to an appropriate licensed professional.

Always read your current state candidate information bulletin and state barber law text. Regulations vary by state and are updated; the version in effect on your exam date is the authoritative source.