Dry skin is a barrier issue, not just a surface issue with a lack of moisture. The outer layer (stratum corneum) is not holding onto moisture like it should be, which is why using a hydrating serum under your moisturizer can make a huge difference. The skin-science behind this is quite simple. Serums have an incredibly light, water-based formula that absorbs quickly into the skin while delivering active humectants, such as hyaluronic acid and glycerin which draw moisture into the cells of the skin. In contrast, moisturizers provide a barrier to keep the moisture within the skin by being occlusive (preventing moisture from passing through) and emollient (softening the outer layer). Therefore, if you skip the serum and go straight to the moisturizer, you are only locking in the existing moisture on your skin. By layering the serum underneath the moisturizer, you can first super-hydrate your skin, and then lock-in that moisture with the moisturizer. For my patients who have dry skin , I tell to look for serums with hyaluronic acid and glycerin as the base humectants, then follow with a moisturizer that contains ceramides. Ceramides are lipids that naturally exist in your skin barrier, replenishing them topically helps restore barrier integrity over time, not just temporarily hydrate. The most common mistake I see? Applying serum to completely dry skin and then waiting too long before moisturizing. Humectants work best applied to slightly damp skin, right after cleansing, and you want to follow immediately with your moisturizer while the skin is still a little tacky. Waiting lets that moisture evaporate before you've had a chance to seal it in, which defeats the purpose entirely. Another mistake includes using a serum with a heavy fragrance or alcohol base, which can further compromise a dry or sensitive barrier. Patiens need to keep the routine simple with a good humectant serum, a ceramide-rich moisturizer, and consistent application which is more effective than layering multiple products that work against each other. Dr. Cho Seung Jun, Dermatolgist at Reberry Clinic
"For people with dry skin, using a hydrating serum before a moisturizer can significantly improve how well the skin retains moisture," says Dr. Sneha Sood, MD (Dermatology), dermatologist at Dr. Sood Aesthetics, Gurgaon. "Hydrating serums commonly contain humectants such as hyaluronic acid and glycerin, which attract water and help increase hydration in the outer layer of the skin. When a moisturizer is applied afterward, it forms a protective layer that helps keep that moisture from evaporating. Ingredients like ceramides, cholesterol, and fatty acids are especially helpful because they support the skin barrier and reduce dryness over time. A useful tip is to apply the serum while the skin is slightly damp and follow it immediately with a moisturizer so the hydration can be sealed in. One common mistake is combining this routine with strong exfoliating acids or alcohol-based products, which may worsen dryness. When done correctly, this simple layering method helps maintain smoother, healthier, and more resilient skin."