What does a moisturiser actually do??

Pick up any moisturiser and the label will throw words at you — "hydrates," "nourishes," "restores barrier function."

Sounds right. Feels reassuring.

But here’s the problem: most of us have no way of knowing whether it’s actually doing any of that — or how we’d even begin to tell.

The ingredients list is hard to read. The claims are vague. And without knowing what a moisturiser is supposed to do in the first place, there’s no way to judge whether yours is doing it.

So before we get to whether a moisturiser is working, we need to start with what it’s actually designed to do.

The problem your moisturiser is solving

Your skin loses a small amount of water every day through evaporation.

This is called transepidermal water loss (TEWL) — which simply means water escaping from your skin into the air.

This happens all the time, even when your skin feels normal.

What determines how noticeable this loss is comes down to your skin barrier.

Your skin barrier is the outermost layer of your skin — a structure of tightly packed skin cells held together by a natural mixture of fats and proteins. Think of it as a seal that helps keep water in.

This barrier is always working.

But your skin barrier doesn’t always slow this loss as much as your skin needs.

This is where a moisturiser comes in.

A moisturiser doesn’t replace your skin barrier — it supports it.

It helps strengthen that surface layer and slows how quickly water escapes, so your skin can hold onto moisture more effectively.

Without that support — or if the moisturiser you’re using doesn’t provide the right balance — your skin barrier can’t hold onto water as well as it should.

That’s when your skin starts to feel dry, tight, or look dull.

In simple terms, a moisturiser does two things:

Increases the water content in your skin

Slows how quickly that water escapes

Everything else a moisturiser does builds on this.

Three ingredients, three different jobs

Most moisturisers work through three types of ingredients — each doing something different.

Humectants draw water into your skin. Common examples include glycerin and hyaluronic acid.

Emollients smooth and soften your skin by filling the small gaps between skin cells. Squalane and shea butter are typical examples.

Occlusives form a light layer on the surface that slows water from escaping back out. Dimethicone and petrolatum are among the most common.

A well-formulated moisturiser contains a combination of all three.

The humectants bring water in. The emollients improve how your skin feels and behaves. The occlusives help keep that water from leaving again.

How to choose what your skin actually needs

For most people, a moisturiser with a good mix of all three ingredient types is enough for day-to-day use.

There is one situation where you might need something more.

If your skin is lacking water (dehydrated), a moisturiser on its own may not be enough to add that hydration.

In that case, applying a hydrating serum first, then a moisturiser on top, works better.

The serum adds water. The moisturiser helps keep it in.

But for most people, most of the time, a well-formulated moisturiser already does both jobs well.

What this means for you

A moisturiser helps increase the water content in your skin and slows how quickly that water escapes — by supporting your skin barrier.

That’s what it’s designed to do, and everything else you see on the label builds on this.