Product Knowledge, Ingredients and Cosmetic Science
What this domain tests
Product knowledge questions test INCI reading, ingredient function, pH, formulation compatibility, preservatives, allergens, claims and client-specific recommendations.
Core rules and concepts
- INCI lists ingredients in descending order above 1%; below 1% the order is flexible.
- Surfactants clean; humectants attract water (glycerin, hyaluronic acid); emollients soften (triglycerides, esters); occlusives reduce water loss (petrolatum, dimethicone).
- Emulsifiers combine oil and water; fatty alcohols such as cetearyl alcohol are emulsifiers or emollients, not drying alcohols.
- Actives include retinoids, niacinamide, AHAs such as glycolic and lactic acid, BHAs such as salicylic acid, vitamin C and peptides; efficacy depends on concentration, pH, stability and delivery.
- Preservatives are necessary in water-containing products; phenoxyethanol is common. Fragrance and essential oils are frequent allergens.
- Natural and clean are marketing terms, not safety guarantees.
- Patch test and advise gradual introduction; avoid mixing incompatible actives.
Worked example
A label reads: Aqua, glycerin, cetearyl alcohol, caprylic/capric triglyceride, niacinamide, phenoxyethanol. Reasoning: glycerin is a humectant; cetearyl alcohol is an emulsifier and emollient; triglyceride is an emollient; niacinamide is a barrier-support active; phenoxyethanol is a preservative. The product is not alcohol-free in the drying-alcohol sense, but the fatty alcohol is not a problem.
Traps that cost marks
- Equating alcohol-free with no fatty alcohols.
- Assuming natural means non-allergenic.
- Ignoring pH when recommending acids.
- Claiming a cream replaces collagen.
- Recommending multiple new actives at once.