Dryness & Dehydration

A 2021 systematic review of dry skin found it is consistently linked to reduced ceramide levels, disrupted natural moisturising factors, and impaired stratum corneum lipid organisation: the layered lipid structure that normally keeps water inside the skin and irritants out.

Once that lipid matrix is depleted, water escapes through the skin faster than it can be replaced (a process called transepidermal water loss), which is why dry skin often feels tight shortly after cleansing. Because ceramides make up such a large share of that lipid matrix, replacing them directly is one of the most well-evidenced ways to help replenish it.

This distinction matters because "dry" and "dehydrated" are often used interchangeably but describe different things: dryness is a skin type, driven by naturally lower oil (sebum) production, while dehydration is a temporary state that can affect any skin type, including oily skin, once the lipid barrier is compromised by weather, over-cleansing, or harsh actives. Both can express the same visible signs, which is why barrier-focused ingredients tend to help either way.

Environmental factors compound this: low humidity, wind, indoor heating, and hot showers can all accelerate transepidermal water loss, which is part of why dryness is often more noticeable in winter regardless of skin type. Using multiple strong actives at once can also strip lipids faster than skin can replenish them, turning mild dryness into a more persistent barrier problem.

Because the underlying issue is a depleted lipid matrix rather than simply "not enough moisture," formulas that combine ceramides with humectants (ingredients like hyaluronic acid that draw water into skin) tend to work better together than either approach alone. The humectant helps bring water in, and the ceramides help support holding it there.

In practice, that means checking a formula for both ceramides and a humectant rather than judging "hydrating" claims by texture alone. A rich-feeling cream isn't automatically more effective than a lighter one if it's missing the lipids skin actually needs to hold moisture in.