Emollient Science — SCE Dermatology MCQ
Instant feedback + full explanation. One question, done properly.
Educational content. Not a substitute for clinical judgement or local policy.
Reveal the answer and explanation
Correct answer: A — Humectants (urea, glycerin) draw water into the stratum corneum from below; occlusives (petrolatum, paraffin) form a lipid barrier preventing transepidermal water loss — many emollients combine both mechanisms
Emollients work through two main mechanisms: (1) Humectants — hygroscopic substances (urea, glycerin, hyaluronic acid, lactic acid) that attract and bind water into the stratum corneum, increasing hydration from the dermal-epidermal water gradient. (2) Occlusives — lipid-rich substances (white soft paraffin/petroleum jelly, liquid paraffin, dimethicone) that form a hydrophobic barrier on the skin surface, reducing transepidermal water loss (TEWL). Many commercial emollients combine both mechanisms for optimal efficacy. Emollient ointments (e.g., 50:50 white soft paraffin/liquid paraffin) are predominantly occlusive; cream-based emollients containing urea combine both. Understanding these mechanisms helps match emollient choice to patient skin type and preference.
Reference: BAD Emollient Guidelines; NICE CG57