Lesson 1Humectants: examples (glycerin, propanediol, sodium PCA), mechanism and suitability for sensitive skinThis section analyses humectants such as glycerin, propanediol, and sodium PCA, describing water-binding mechanisms, synergy in blends, impact on skin feel, and how to tailor humectant systems for sensitive or compromised barriers.
Glycerin: benchmark humectant behaviourPropanediol and alternative glycolsSodium PCA and NMF-mimicking blendsTack reduction and sensory balancingHumectants in barrier-impaired skinLesson 2Antioxidants and chelators: examples (tocopherol, EDTA), role in oxidative stability and preservationThis section explains how antioxidants and chelators, including tocopherol and EDTA, protect oils and actives from oxidation, support preservative systems, and extend shelf life without compromising skin comfort or clarity.
Lipid-phase antioxidants for oilsWater-phase antioxidants and synergyChelators to control trace metalsImpact on colour and odour stabilityDesigning antioxidant systems in O/WLesson 3Occlusives: examples (dimethicone, hydrogenated polyisobutene), balancing occlusion and light feelThis section discusses occlusives such as dimethicone and hydrogenated polyisobutene, showing how to balance barrier reinforcement, transepidermal water loss reduction, and a light, breathable feel suitable for daily sensitive skin care.
Dimethicone grades and skin feelHydrogenated polyisobutene in creamsTEWL reduction and barrier metricsAvoiding heaviness and pore occlusionOcclusive levels for day versus nightLesson 4Soothing/anti-irritant actives: examples (niacinamide, panthenol, dipotassium glycyrrhizate), evidence and typical use rangesThis section examines soothing and anti-irritant actives such as niacinamide, panthenol, and dipotassium glycyrrhizate, summarising mechanisms, supporting evidence, compatibility, and typical use ranges in sensitive skin moisturisers.
Niacinamide: barrier and redness benefitsPanthenol: hydration and repair rolesDipotassium glycyrrhizate: calming actionUse levels and pH compatibilityCombining soothing actives safelyLesson 5Core functional groups for O/W moisturiser: role of solvent, humectant, emollient, occlusive, emulsifierThis section maps the core functional groups in O/W moisturisers—solvents, humectants, emollients, occlusives, and emulsifiers—showing how each contributes to feel, hydration, stability, and tolerance in sensitive skin formulations.
Water phase and co-solvent selectionHumectant blend design and levelsEmollient phase structure and feelOcclusive agents and barrier supportEmulsifier system and phase balanceLesson 6Preservative systems for mild formulas: examples (phenoxyethanol+ethylexylglycerin, sodium benzoate+potassium sorbate), rationale for sensitive skinThis section reviews preservative systems suited to mild O/W moisturisers, such as phenoxyethanol with ethylhexylglycerin and organic acid salts, focusing on spectrum, pH needs, regulatory limits, and sensitive skin tolerability.
Phenoxyethanol and boosters in blendsSodium benzoate and potassium sorbatepH windows for organic acid systemsPreservative efficacy versus mildnessMinimising sting and sensitisation riskLesson 7Emollients: examples (caprylic/capric triglyceride, C12-15 alkyl benzoate), sensory and absorption considerationsThis section explores emollient choices such as caprylic/capric triglyceride and C12-15 alkyl benzoate, linking chemical structure to spread, absorption rate, residue, and suitability for lightweight, non-greasy sensitive skin creams.
Medium-spreading esters and triglyceridesFast-absorbing versus rich emollientsPolarity and pigment or filter wettingTack, gloss, and afterfeel controlEmollient choices for acne-prone skinLesson 8Solubilisers, pH adjusters, and texture modifiers: examples and impact on performanceThis section reviews key solubilisers, pH adjusters, and texture modifiers used in O/W moisturisers, explaining how they influence clarity, viscosity, spreadability, and overall performance while maintaining comfort on sensitive skin.
Nonionic solubilisers for fragrance and oilspH adjustment for skin compatibilityBuffers and pH drift controlRheology modifiers and viscosity tuningSlip, spread, and pick-up optimisationLesson 9Common incompatibilities and ingredient substitution strategiesThis section covers common incompatibilities in O/W moisturisers, including pH, charge, and oxidation issues, and presents practical substitution strategies to maintain stability, mildness, and performance when changing suppliers or actives.
pH-driven instability and hydrolysisCationic–anionic charge conflictsOxidation-prone oils and activesPreservative and polymer conflictsDesigning robust substitution plansLesson 10Emulsifiers and co-emulsifiers: examples (polyglyceryl esters, glyceryl stearate SE), HLB considerations and mildnessThis section details emulsifiers and co-emulsifiers, including polyglyceryl esters and glyceryl stearate SE, explaining HLB concepts, required HLB of oil phases, and how to design mild, stable systems for sensitive skin moisturisers.
Required HLB of the oil phaseNonionic emulsifiers for mildnessPolyglyceryl esters in O/W systemsFatty alcohols as co-emulsifiersOptimising droplet size and stability
