Product Knowledge and Cosmetology Science
Core concepts
Know the structure of hair: cuticle (outer protective layer), cortex (main body, contains pigment and disulphide bonds), and medulla (central core, not always present). Understand the hair growth cycle: anagen (growth), catagen (transition), telogen (resting/shedding). Know that hair is mostly keratin and that its pH and disulphide bonds govern chemical behaviour.
Know product categories and functions: shampoos, conditioners, treatments, styling products, colour, perming and straightening products, and their key ingredients. Understand surfactants, humectants, silicones, polymers, and preservatives. Know why pH matters for cuticle condition and colour retention.
Know safety and labelling: read labels, follow dilution and contact times, check expiry, and store correctly. Understand patch testing and allergy basics.
Traps
Questions often confuse the cortex with the cuticle, or assume all silicones are damaging. Another trap is ignoring pH when choosing products for coloured or chemically treated hair.
Rule of thumb
Match the product to the hair's structure and condition: cuticle health and pH drive the result.