Retinol Plus Mask

These describe what an ingredient is, not whether it is a problem. The stance marks above are the ratings; these are not.

• common irritantPropylene Glycol

  • Propylene Glycol: A solvent that shows up in patch-test clinics, more often as irritation than as allergy. American Contact Dermatitis Society, Allergen of the Year 2018 (Jacob SE, Scheman A, McGowan MA, Dermatitis 2018;29(1):3-5).

• exfoliating acidSalicylic Acid

  • Salicylic Acid: A beta hydroxy acid that clears the inside of pores; the EU restricts its level and keeps it off children under three. SCCS Opinion on Salicylic Acid, Submission I (SCCS/1601/18, corrigendum of 20 to 21 June 2019); EU Regulation (EC) 1223/2009 Annex III entry 98, as amended by Commission Regulation (EU) 2021/850, which for purposes other than preservation caps it at 3,0% in rinse-off hair products, 2,0% in other products, and 0,5% in body lotion, eye shadow, mascara, eyeliner, lipstick and roll-on deodorant, and states "Not to be used in preparations for children under 3 years of age." Its separate PRESERVATIVE use sits at Annex V entry 3, capped at 0,5% (acid), where the salts carry the carve-out "except for shampoos".

• retinoidRetinol

  • Retinol: A vitamin A derivative that speeds skin turnover; dryness and flaking while skin adjusts are its usual accompaniment. SCCS Opinion on Vitamin A (Retinol, Retinyl Acetate, Retinyl Palmitate), SCCS/1576/16, final version of 6 October 2016; Commission Regulation (EU) 2024/996 added the group to EU Regulation (EC) 1223/2009 Annex III entry 376, capping it at 0,05% retinol equivalent in body lotion and 0,3% in other leave-on and rinse-off products, with the label statement "Contains Vitamin A. Consider your daily intake before use."

• humectantGlycerin, Sodium Hyaluronate

  • Glycerin: A humectant, and one of the two ingredients a comparison of moisturiser components found made a significant difference to skin hydration. FDA OTC skin protectant monograph, 21 CFR 347.10(h), lists glycerin as a skin protectant at 20 to 45%. On the humectant half: Jeong CB, Han JY, Cho JC, Suh KD, Nam GW, "Analysis of electrical property changes of skin by oil-in-water emulsion components", Int J Cosmet Sci 2013;35(4):402-410, DOI 10.1111/ics.12059, PMID 23621673, found that "glycerine and urea showed significant skin hydration effects compared with other humectants".
  • Sodium Hyaluronate: A humectant that holds a large amount of water at the skin surface. Chylińska N, Maciejczyk M, "Hyaluronic Acid and Skin: Its Role in Aging and Wound-Healing Processes", Gels 2025;11(4):281, DOI 10.3390/gels11040281, PMID 40277717, open access: hyaluronic acid's "high osmotic activity and anionic structure enable it to bind large amounts of water", and "sodium and potassium hyaluronate are widely used in moisturizing products". The same review notes that high-molecular-weight hyaluronic acid does not penetrate the deeper layers.

• barrier lipidCeramide 2, Linoleic Acid

  • Ceramide 2: One of the lipid families the skin barrier is actually built from. Feingold KR and Elias PM, "The role of ceramides in the disruption of the cutaneous permeability barrier, a common manifestation of skin disorders", J Lipid Res 2024;65(8):100593, DOI 10.1016/j.jlr.2024.100593, open access: the barrier lipid matrix "by weight is approximately 50% ceramides, 25% cholesterol, and 15% free fatty acids".
  • Linoleic Acid: An essential fatty acid the skin barrier uses and cannot make for itself. Khnykin D, Miner JH, Jahnsen F, "Role of fatty acid transporters in epidermis", Dermatoendocrinol 2011;3(2):53-61, DOI 10.4161/derm.3.2.14816, open access: "The human body can produce all but two of the fatty acids it needs: linoleic acid (C18:2, n6) and alpha-linolenic acid (C18:3, n3)", and replacing linoleic acid with a non-essential fatty acid "will lead to barrier defects". Feingold and Elias, J Lipid Res 2024: linoleate "is required for the synthesis of a subgroup of acylceramides".

• soothingBisabolol

  • Bisabolol: The main soothing component isolated from chamomile. Eddin LB et al., "Health Benefits, Pharmacological Effects, Molecular Mechanisms, and Therapeutic Potential of alpha-Bisabolol", Nutrients 2022;14(7):1370, DOI 10.3390/nu14071370, PMID 35405982, open access: it "is integrated in many cosmetic formulations due to its skin soothing effects, well documented dermal absorption and the absence of dermal irritations or photosensitivity following its application". The EMA HMPC assessment report on Matricaria recutita (EMA/HMPC/55837/2011) discusses its anti-inflammatory data.