This one is an either/or question we get asked often enough that it deserves a straight answer rather than a "why not both" shrug. Here's what each product is built to do, and why the answer is both, in a specific order.
Serum and moisturiser get seen as competing purchases, as if one is the "serious" upgrade and the other is optional once you have it. They're not competing. They're built to do two different, non-overlapping jobs, and skipping either one means the other can't fully do its job either.
What a serum is built to do
A serum is formulated to deliver a concentrated dose of active ingredients as efficiently as possible. That usually means a lighter, water- or gel-based texture that sinks in quickly, with a higher share of the ingredients that give it its purpose. Serums generally don't contain much in the way of occlusive ingredients, so they're not designed to lock moisture in on their own.
What a moisturiser is built to do
A moisturiser's job is structurally different: hold water in the skin and reinforce the barrier that keeps it there. Moisturiser formulas typically combine three ingredient categories: humectants (like hyaluronic acid or glycerin) that draw water into the skin, emollients that smooth and soften, and occlusives (like ceramides, shea butter, or plant oils) that form a layer to reduce water loss through the surface. A widely cited review by Lodén, published in the American Journal of Clinical Dermatology, describes how moisturisers combine humectants, emollients and occlusive ingredients to soften skin and reduce water loss from its surface. That's the whole distinction in one sentence: a serum delivers, a moisturiser seals and protects.
Why the order matters
Skincare layers thinnest to thickest, and there's a mechanical reason for it. If moisturiser goes on first, its occlusive ingredients sit on the surface and form exactly the kind of barrier a serum is trying to get through. The serum's active ingredients end up doing very little as a result. Applied the other way round, serum first onto clean, slightly damp skin, moisturiser second, the serum's actives reach skin while it's still permeable, and the moisturiser then does its real job of holding that hydration in and stopping it from evaporating straight back out. Reverse the order and you're not getting a stronger effect from either product: you're getting a weaker one from both.
What this looks like in practice
Take two products already in our range: the Hexapeptide Smoothing Serum and the Ceramide Cocoon Night Cream. Applied serum first, the silky serum goes straight onto clean skin, and the richer cream then wraps everything in comfort overnight. Reverse them and the cream's shea and cocoa butter get there first, so the lighter serum has a harder time spreading evenly onto skin.
For hydration specifically (which is the pairing people usually mean when they ask this question), the same order applies. A hyaluronic acid serum applied first draws water into skin at the surface; a moisturiser with occlusive ingredients applied afterwards locks that water in rather than letting it evaporate over the next hour. Our Multi-Weight HA Hydrating Serum is built around hyaluronic acid, and it also features in our Weightless Hydration Gel, Hexapeptide Smoothing Serum and Sun Protect Tinted Fluid SPF30. The same serum-then-moisturiser logic applies whichever hyaluronic acid products you use.
Products that blend the two
Not every product sits neatly on one side of this line. Some serums include a light occlusive to offset dryness from a strong active (a retinol serum with added squalane, for example) and some moisturisers carry an active concentration high enough to do real active work in their own right, not just sealing. When a product blurs the categories, its texture and place in your routine matter more than what it's labelled: if it's designed to be followed by something richer, use it like a serum and apply it first; if it's the last, heaviest step you use, use it like a moisturiser regardless of which actives it happens to contain.
How the order changes between morning and evening
The serum-then-moisturiser sequence holds in both routines, but what you're layering often differs. Mornings tend to prioritise protective actives (an antioxidant like vitamin C is a common choice), finished with a moisturiser and then SPF as the final, non-negotiable step, since sunscreen needs to sit on top to do its job rather than underneath other products. Evenings are typically when stronger actives come out, since they're the ones most likely to increase sun sensitivity, followed by a richer moisturiser or a dedicated night formula to support the skin while you sleep. The underlying logic doesn't change between the two: whatever is delivering an active goes on first, and whatever is holding moisture in and protecting the barrier goes on last.
Do you need both, or just one
If your goal is simply "keep skin comfortable and stop it feeling dry," a good moisturiser alone can do a reasonable job on its own. It's not nothing. But a moisturiser alone can't deliver a concentrated active the way a serum can, and a serum alone will lose most of its hydrating or active benefit to evaporation and barrier permeability without something sealing it in afterwards. If you're only ever going to buy one, moisturiser is the more defensible single purchase for basic skin comfort. If you have something specific in mind, such as extra hydration or a brighter-looking complexion, a serum is where to look, with a moisturiser on top.
In short
This was never really an either/or question. It's a sequencing question that got mistaken for a shopping question. Serum first, on clean skin, while it's most permeable. Moisturiser second, to hold what the serum delivered and support the barrier around it. If you're starting from nothing, our Hexapeptide Smoothing Serum and Ceramide Cocoon Night Cream are a currently-available example of the pairing, but the principle applies to any well-formulated serum-and-moisturiser combination, ours or otherwise.
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The short version
Serum and moisturiser aren't competing purchases. They do two different jobs in a specific order. Here's what each is actually formulated to do, and why skipping one weakens the other.
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