For optimal efficacy, skincare products should be applied based on molecular weight and solubility, generally following a 'thinnest-to-thickest' rule. Serums, which are typically water-based and highly concentrated with active molecules like L-ascorbic acid or niacinamide, must be applied first to clean, slightly damp skin. This ensures that these small molecules can penetrate the stratum corneum without being blocked by heavier occlusive agents [1]. Applying water-based serums over oils significantly reduces their flux through the skin, rendering expensive actives less effective [2].
Once serums have been absorbed, a moisturiser should be applied. Moisturisers serve a dual purpose: they provide humectants like glycerin to draw water into the epidermis and emollients to smooth the skin surface [3]. In the Australian climate, where high UV exposure and low humidity can compromise the skin barrier, the moisturiser acts as a crucial 'seal' for the hydration provided by the serum. If you choose to use a facial oil, it should be applied last or mixed into your moisturiser. Oils are lipophilic and often contain larger molecules that create a hydrophobic film, designed to lock in moisture and prevent transepidermal water loss (TEWL) [4].
The science of layering is rooted in the principles of percutaneous absorption and the partition coefficient of active ingredients. The stratum corneum, the skin's outermost layer, acts as a lipophilic barrier that regulates the entry of topically applied substances. For an active ingredient to reach its target site, it must successfully partition from the product vehicle into the skin's lipid bilayer [1].
Formulation science dictates that water-soluble actives require a clear pathway to the skin. If a heavy, occlusive oil or a thick petrolatum-based moisturiser is applied first, it creates a physical barrier that prevents subsequent water-based formulations from reaching the skin surface. Furthermore, the pH of products must be considered; applying a high-pH moisturiser immediately after a low-pH Vitamin C serum can neutralise the acid, potentially reducing its clinical biological activity [5].
To respect this delicate layering sequence, many individuals find that starting with a lightweight, high-performance serum like Cellular Thread allows its peptide complex and Kakadu Plum to penetrate effectively before sealing the skin with a more occlusive layer. Following this with a lipid-rich moisturiser such as Cellular Crème ensures that the previous active ingredients are locked in, providing a final barrier that supports long-term firmness and hydration.
FAQ
Can I mix my oil directly into my moisturiser?
Yes, mixing a few drops of oil into your moisturiser is an effective way to boost the emollient properties of your cream without compromising the absorption of your serums. This technique, often referred to as 'buffer layering', helps to enhance the lipid profile of the moisturiser, making it particularly beneficial for those with dry or mature skin types in the arid Australian environment [3][4].
Does the order change if I am using a prescription retinoid?
Prescription retinoids are potent and can be irritating. While the standard order is serum then retinoid, many dermatologists recommend the 'sandwich method'—applying a thin layer of moisturiser, then the retinoid, then another layer of moisturiser—to minimise irritation without significantly reducing the retinoid's long-term efficacy in treating photo-ageing [2][6].
Should sunscreen be applied before or after my facial oil?
Sunscreen must always be the final step of your skincare routine, applied after your oil or moisturiser has fully settled. Applying oil over sunscreen can dissolve the UV filters and disrupt the uniform film required for effective protection, leaving your skin vulnerable to UV-induced damage [7].
References:
[1] Roberts MS, et al. Human skin morphology and dermal absorption. Toxicology and Applied Pharmacology. 2021;411:115351. doi:10.1016/j.taap.2020.115351.
[2] Benson HAE. Skin Electroporation and Sonophoresis in Transdermal Drug Delivery. Current Drug Delivery. 2005;2(4):389-405. doi:10.2174/156720105774370167.
[3] Rawlings AV, et al. Moisturizers and skin barrier function. Dermatologic Therapy. 2004;17(s1):43-48. doi:10.1111/j.1396-0296.2004.04s1005.x.
[4] Ghadially R, et al. The aged epidermal permeability barrier. Structural, functional, and lipid biochemical abnormalities in humans and a senescent murine model. Journal of Clinical Investigation. 1995;95(5):2281-90. doi:10.1172/JCI117919.
[5] Schmid-Wendtner MH, Korting HC. The pH of the skin surface and its components. Skin Pharmacology and Physiology. 2006;19(6):296-302. doi:10.1159/000094670.
[6] Mukherjee S, et al. Retinoids in the treatment of skin aging: an overview of clinical efficacy and safety. Clinical Interventions in Aging. 2006;1(4):327-348. doi:10.2147/ciia.2006.1.4.327.
[7] Geoffrey K, et al. Sunscreen products: Rationale for use, formulation development and regulatory considerations. Saudi Pharmaceutical Journal. 2019;27(7):1009-1018. doi:10.1016/j.jsps.2019.08.003.
Medical Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting any new skincare regimen. Content reviewed by a biomedical scientist.
