Cosmetology Science: Anatomy, Physiology, Chemistry and Cosmetic Products
What this domain tests
This section links basic anatomy, physiology and chemistry to salon work. Expect skin and hair structure, bones and muscles, pH, solutions, emulsions and product ingredients.
Core rules
- Skin has epidermis, dermis and subcutaneous layers. Hair grows from the follicle; the nail grows from the matrix. These structures explain service limits and contraindications.
- Know the main facial bones and muscles, nerve and blood supply. This supports massage, facial and shaving safety.
- pH runs from 0 to 14. Acids are below 7, alkalis above 7 and neutral is 7. Hair and skin prefer mildly acidic products around pH 4.5–5.5.
- Surfactants clean, humectants attract water, emollients soften and preservatives limit microbial growth. Emulsions are oil-in-water or water-in-oil.
- Mix chemicals only as directed. Never combine household cleaners or add water to concentrated product incorrectly.
Worked example
A relaxer has pH 12 and a shampoo has pH 5. Reasoning: the relaxer is strongly alkaline, so it swells the cuticle and breaks disulphide bonds. The acidic shampoo helps close the cuticle and restore smoothness after rinsing. Calling both “neutral” because they feel mild is wrong; pH is measured, not felt.
Traps
Do not confuse neutral pH with a neutraliser; do not assume water is always ideal for hair; do not mix products casually; do not ignore preservatives in water-containing products.