"Moisturising" sounds like one simple step, but it's actually three different jobs done by three different types of ingredient. Understanding the difference between humectants, emollients and occlusives is the key to choosing a moisturiser that actually suits your skin — and to working out why a product that's perfect for a friend leaves yours greasy or still tight.
The three ways a moisturiser works
Every good moisturiser is really a blend of three mechanisms: pulling water into the skin, smoothing and refilling the gaps between skin cells, and sealing the whole thing so moisture doesn't escape. Those three jobs belong to humectants, emollients and occlusives respectively.
Humectants: attract water
Humectants draw water into the upper layers of the skin — either up from the deeper layers or, in a humid environment, from the air. Common examples are glycerin, hyaluronic acid, panthenol and urea. They're what make skin feel instantly plump and hydrated. One important catch: in dry air, a humectant with nothing on top of it can actually pull water out of the skin and let it evaporate. That's why humectants work best when sealed in by the other two types.
Emollients: smooth and soften
Emollients fill the microscopic gaps between skin cells, replacing missing lipids and leaving the surface soft, smooth and supple. This is the category that makes skin feel nice. Examples include ceramides, squalane, jojoba oil, fatty acids and dimethicone. Because they top up the skin's own lipids, emollients also quietly support the barrier — ceramides being the standout example.
Occlusives: seal it in
Occlusives form a protective layer on the surface that physically slows water loss (what scientists call transepidermal water loss). They're the "lid on the jar". Petrolatum is the most effective, and others include mineral oil, lanolin, beeswax, squalane and dimethicone. Applied over a humectant, an occlusive locks in the water that humectant attracted — which is the whole logic of layering.
Think of it as a sequence: a humectant brings the water, an emollient smooths the surface, and an occlusive seals it in. The best moisturisers do all three.
How to choose for your skin
A well-formulated cream already balances the three, but you can tilt the balance to suit you. Oily or acne-prone skin usually does well with a lighter, humectant-rich gel and a light emollient like dimethicone — enough to hydrate without feeling heavy. Dry skin benefits from richer emollients and a more occlusive finish to hold moisture in. Dehydrated skin (which lacks water rather than oil, and can happen even to oily types) wants plenty of humectants plus something to seal them. For the classic layering approach, apply a humectant serum onto slightly damp skin, then a moisturiser with emollients and occlusives on top.
The verdict
There's no single "best" moisturiser — only the right balance of humectant, emollient and occlusive for your skin and your climate. Once you can read a product through that lens, choosing one (and understanding why it works) becomes far easier than the label suggests.
This article is for general education and is not medical advice.
References
Sethi A, Kaur T, Malhotra SK, Gambhir ML. Moisturizers: the slippery road. Indian Journal of Dermatology, 2016.
Purnamawati S, Indrastuti N, Danarti R, Saefudin T. The role of moisturizers in addressing various kinds of dermatitis: a review. Clinical Medicine & Research, 2017.
Draelos ZD. The science behind skin care: moisturizers. Journal of Cosmetic Dermatology, 2018.