Moisturizer vs. Serum: What Your Skin Needs in Winter

Serum and moisturizer are not rivals. They do different jobs, and winter is the season when you most need both.

They Do Different Jobs

"Serum or moisturizer?" is a slightly misleading question, because the two are built to do different things. Dermatology literature sorts moisturizing ingredients into a few classes by how they work: occlusives sit on the surface and slow water loss, humectants attract and bind water, and emollients smooth and soften the skin^[1]. Most moisturizers combine all three. Most hydrating serums lean heavily on the humectant side.

What Winter Changes

In low humidity, skin loses water faster and its water-holding capacity drops^[2]. That makes both jobs matter more. A humectant can only hold water that is actually present, and without something to slow evaporation, much of it can be lost again. Reviews of the barrier describe moisturizers as working on several levels at once: occluding the surface, drawing water into the epidermis, and supporting the lipid layer^[3].

How to Layer Them in Winter

• Apply your hydrating serum first, on slightly damp skin, so humectants have water to bind.
• Follow with a moisturizer to seal that hydration in, especially at night and in dry, heated rooms.
• If your skin is oily, use a lighter gel-cream rather than skipping the moisturizing step.
• If skin is very dry, add a richer occlusive layer on the driest areas only.
• In the morning, finish with sunscreen as the last step.