Cosmetology Products, Ingredients and Contraindications
Cosmetology Products, Ingredients and Contraindications
This domain tests ingredient function, product selection, patch testing and when not to use a product. The exam rewards safety over sales.
Core rules
- Surfactants clean; humectants attract water (glycerin); emollients soften (oils, fatty alcohols); occlusives seal (petrolatum); preservatives prevent microbial growth; pH affects stability and tolerance.
- Check the label for actives and warnings. Common actives include AHAs/glycolic acid, BHA/salicylic acid, retinol, vitamin C, hydroquinone, benzoyl peroxide and essential oils. Each has a specific contraindication profile.
- Patch-test new colour, wax, lash glue and skincare 24–48 hours before, behind the ear or inner elbow, and record the result.
- Do not apply acids, retinoids or strong exfoliants to broken, inflamed, sunburnt or recently waxed skin. Avoid hydroquinone in pregnancy; avoid essential oils on sensitive skin or in high dilution.
- Never mix products unless the manufacturer states it is safe; do not add water to a product; respect expiry and period-after-opening.
Worked example
A client books a glycolic peel but mentions she started prescription retinol last week and waxed her upper lip two days ago. Reasoning: retinol thins the stratum corneum and recent waxing removes surface cells; an acid peel could cause burns and post-inflammatory hyperpigmentation. The correct action is to postpone the peel, advise barrier repair and sun protection, and rebook after the skin has settled.
Traps
- Assuming 'natural' or 'ayurvedic' means allergy-free.
- Skipping a patch test because the client has had the brand before.
- Using expired product to avoid waste.
- Diagnosing an allergy instead of referring.
- Mixing bleach and ammonia or other incompatible chemicals.