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34 ASCP Skin Deep Spring 2026 factors like pollution. Vitamin C incites fibroblast activity to strengthen elasticity. Although the activity of collagen production is found in the dermis, with a more effective delivery system, vitamin C is more stable and yields better results. AHAS AND BHAS Alpha and beta hydroxy acid serums provide additional exfoliation and treatment options. It's important to diff erentiate between AHA and BHA molecular size as it often takes on the aforementioned idea that the smaller the molecule ingredient the better. This falsehood can lead to overexfoliation due to the eff ects of delivery through the epidermis. Additionally, the molecular size can have a direct correlation with eff ects on the sensation of the skin. AHA Following are examples of common AHA serums: • Glycolic acid can penetrate through the structure of the cells, assisting with texture, brightening, and overall exfoliation. • Lactic acid is a large molecule that signals hydration from the dermis to move toward the stratum corneum, hydrating the epidermis. This large molecular acid allows for gentler exfoliation, targeting dry, dehydrated, and aging skin. • Mandelic acid is larger than lactic and glycolic acids and has a slower penetration through the stratum corneum, making it a gentler exfoliation experience. BHA Salicylic acid, the most common BHA, is a drying exfoliant that targets excess oil and sebum. This acid is best for oil control or acne-prone skin. This acid can follow a transappendageal path to fi ghting acne, drying oil, and drying sebum while exfoliating the skin. SKIN PHYSIOLOGY A NEW KNOWLEDGE OF SERUMS Eff ective serum delivery systems are not determined by molecular size alone but by how the product ingredients are formulated and their process for delivery. Understanding the formulation of ingredients allows for you to make better choices to assist your clients with their skin concerns. Note 1. S. A. Rakesh et al., "Nano Face Serums: Unlocking the Power of Nanotechnology for Advanced Skincare," International Journal of Pharmacognosy and Pharmaceutical Research 7, no. 1C (2025): 180–4. doi.org/10.33545/26647168.2025.v7.i1c.109. Resources Bos, J. D., and M. M. Meinardi. "The 500 Dalton Rule for the Skin Penetration of Chemical Compounds and Drugs." Experimental Dermatology 9, no. 3 (June 2000): 165–9. doi.org/10.1034/j.1600-0625.2000.009003165.x. Mélot, M., et al. "Studying the E ectiveness of Penetration Enhancers to Deliver Retinol Through the Stratum Cornum by In Vivo Confocal Raman Spectroscopy." Journal of Controlled Release 138, no. 1 (August 2009): 32–9. doi.org/10.1016/j.jconrel.2009.04.023. GETTY IMAGES