Heyday Serum

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

• humectantGlycerin, Panthenol, 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".
  • Panthenol: A provitamin B5 humectant used in products aimed at irritated and healing skin. On the humectant half: Ferreira VTP, Silva GC, Martin AA, Maia Campos PMBG, "Topical dexpanthenol effects on physiological parameters of the stratum corneum by Confocal Raman Microspectroscopy", Skin Res Technol 2023;29(9):e13317, DOI 10.1111/srt.13317, PMID 37753694, PMCID PMC10504581, open access, Introduction: "As a humectant, it has been shown to retain water more efficiently than other humectants during the last stages of dehydration..." On the soothing half, which that paper does NOT support: Cho YS, Kim HO, Woo SM, Lee DH, "Use of Dexpanthenol for Atopic Dermatitis—Benefits and Recommendations Based on Current Evidence", J Clin Med 2022;11(14):3943, DOI 10.3390/jcm11143943, PMID 35887707, open access, section 3.5: "To facilitate wound healing, dexpanthenol reduces inflammation, and promotes cell proliferation and epithelial remodeling."
  • 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.

• soothingPanthenol

  • Panthenol: A provitamin B5 humectant used in products aimed at irritated and healing skin. On the humectant half: Ferreira VTP, Silva GC, Martin AA, Maia Campos PMBG, "Topical dexpanthenol effects on physiological parameters of the stratum corneum by Confocal Raman Microspectroscopy", Skin Res Technol 2023;29(9):e13317, DOI 10.1111/srt.13317, PMID 37753694, PMCID PMC10504581, open access, Introduction: "As a humectant, it has been shown to retain water more efficiently than other humectants during the last stages of dehydration..." On the soothing half, which that paper does NOT support: Cho YS, Kim HO, Woo SM, Lee DH, "Use of Dexpanthenol for Atopic Dermatitis—Benefits and Recommendations Based on Current Evidence", J Clin Med 2022;11(14):3943, DOI 10.3390/jcm11143943, PMID 35887707, open access, section 3.5: "To facilitate wound healing, dexpanthenol reduces inflammation, and promotes cell proliferation and epithelial remodeling."