Dr. Jane Yoo explains the three types of moisturizer ingredients and how they work. Humectants like glycerin and hyaluronic acid draw water into skin. Emollients such as ceramides smooth and soften. Occlusives like petrolatum seal moisture in. Which you need depends on your skin type and climate.
Hi, I'm Dr. Jane Yoo, board-certified dermatologist and Mohs surgeon. Today I want to break down an important distinction in skincare: the difference between humectants, emollients, and occlusives. Now, these are all considered moisturizers, and these three categories form the foundation of almost every moisturizer you use. Most products actually contain a combination of all three. But each plays a very different role in supporting skin hydration and barrier health. Let's start with humectants. Humectants are ingredients that attract and bind water. They work by drawing moisture into the stratum corneum either from the deeper layers of the skin or from the surrounding environment. Their primary job is to increase the water content of the skin. Common humectants include glycerin, hyaluronic acid, urea, lactic acid, and components of the skin's natural moisturizing factor. These ingredients help the skin look more plump, flexible, and hydrated. However, humectants do not prevent water from escaping the skin on their own. That's why they work best when paired with an emollient or occlusive. In very dry environments, humectants used alone can even increase transepidermal water loss, which is why layering matters. Next are emollients. Emollients are lipid-based ingredients that smooth and soften the skin. They work by filling in the spaces between skin cells in the stratum corneum, helping the surface feel more even and less rough. Emollients also support barrier recovery by improving membrane fluidity and reinforcing the lipid matrix. Examples of emollients include fatty acids, fatty alcohols, triglycerides, esters, ceramides, squalene, and certain silicones. Emollients modestly reduce water loss, but their primary function is to improve texture, comfort, and barrier integrity rather than directly hydrating the skin. Finally, we have occlusives. Occlusives create a physical barrier on the surface of the skin that slows water evaporation. They do not add water to the skin, but they are extremely effective at preventing moisture loss, just like a raincoat. This makes them especially helpful for very dry, compromised, or post-procedure skin. Classic occlusives include petrolatum, dimethicone, lanolin, beeswax, mineral oil, and waxes. Petrolatum in particular is considered one of the most effective occlusives available, capable of significantly reducing transepidermal water loss. Because occlusives can feel heavier, they're often used at night or targeted to areas with severe dryness. So, how do these all work together? An effective moisturizer typically combines all three categories. Humectants draw the water in, emollients smooth and repair the barrier, and occlusives seal everything in. The ideal formulation depends on your skin type, environment, and skin condition. For example, lighter gels and lotions may be better for oily skin or humid climates, while creams and ointments are often more appropriate for people with eczema, xerosis, or barrier disruption. Understanding these roles helps you choose products more intentionally rather than relying on marketing terms like hydrating or moisturizing without knowing what's actually doing the work.
