Skin hydration is one of the most fundamental parts of skincare. Your routine can easily consist of just two steps: 1) a good cleanse followed by 2) a good moisturizer. But do you know how your moisturizer actually works?
The skin barrier and TEWL
The outermost layer of your skin, the stratum corneum, has many protective functions. One of the most important is keeping your skin hydrated by holding on to water and regulating how much of it evaporates.
You can think of this layer as a brick wall. The skin cells are the bricks, and between them is a “mortar” of natural fats (lipids) that seals the gaps. Inside the cells, you’ll find the skin’s own water-binding molecules, known as the natural moisturizing factor (NMF) – a mix of amino acids, lactic acid, urea and salts that hold on to water. On top, a thin film of sebum and sweat, called the hydrolipidic film, adds an extra protective layer.
Your skin is constantly losing a small amount of water, which evaporates from the deeper layers out through the surface. This is called transepidermal water loss, or TEWL. Some water loss is completely normal. But when the skin barrier is weakened – by cold weather, harsh cleansers or simply age – the gaps in the wall grow bigger, more water escapes, and TEWL goes up. The result is skin that feels tight, dry or sensitive.
Your skin’s natural moisturizing factor (NMF)
How much NMF your skin has varies from person to person and depends partly on your genes. But the NMF also decreases with age, and it can be weakened by cold, dry air, sun exposure, harsh cleansers and over-cleansing. When the NMF is low, the skin finds it harder to hold on to water and quickly feels dry and tight.
You can’t change your genes, but you can support your skin by giving it ingredients that resemble its own NMF – and by protecting the water it already has. That’s why a good skincare routine is about more than adding moisture – it’s also about supporting your skin in keeping it. And not just on your face.
Humectants, emollients and occlusives
Creams, lotions, balms and oils can all support your skin’s natural barrier. They’re made of water-soluble ingredients (as in our Niacinamide Lifting Mist), oil-soluble ingredients (as in our Vitamin Face Oil), or both (as in our Daily Hydra Cream). Most moisturizers combine three types of ingredients, each with its own job:
Humectants – attract water
Humectants draw water into the upper layers of the skin and bind it there, much like the skin’s own NMF. Several of them are actually part of the NMF itself, while others, like hyaluronic acid, work alongside it:
Sodium PCA: One of the most important components of the skin’s NMF. In our Intense Hydra Serum and Vitamin Lifting Serum.
Urea: A natural part of the NMF that binds water and moisturizes dry skin. In our Intense Hyaluronic Mask and Intense Peel Mask.
Lactic acid: Binds moisture while gently exfoliating the skin’s surface. In our Intense Peel Mask, Skin Perfector 2% BHA and Skin Perfector SeboClear.
Hyaluronic acid: Hyaluronic acid occurs naturally in the skin, where it binds water and keeps the skin plump and supple. The skin’s own production decreases with age, which is one of the reasons skin can feel drier over time. Applied to the skin, hyaluronic acid works as a humectant: it draws water into the upper layers and holds on to it. The size of the molecule matters. Large molecules stay on the surface and form a moisture-binding film, while smaller molecules reach a little deeper into the skin’s upper layers.
That’s why some of our formulas combine both – including our:
You’ll also find hyaluronic acid in our:
- Daily Hydra Cream and Daily Hydra Cream Sensitive
- 24-Hour Hydra Gel
- Daily Mineral Gel
- Niacinamide Lifting Mist
- Intense Hyaluronic Mask
Our Intense Hyaluronic Mask combines hyaluronic acid with glycerin and urea – one of the reasons it’s a bestseller.
Emollients – soften
Emollients are oil-based ingredients that fill the tiny gaps between the skin cells on the surface. This makes rough, flaky skin feel soft, smooth and supple again. Examples are plant oils, shea butter and squalane.
Occlusives – protect
Occlusives form a thin, protective layer on top of the skin that keeps water from evaporating – and in that way, they lower TEWL. Examples are beeswax, plant waxes and some plant butters. Many ingredients do more than one job: shea butter, for instance, both softens and protects.
This is why applying our Instant Repair Balm, rich in shea butter, plant oils and plant waxes, on very dry and damaged spots is always a good idea.
Dry or dehydrated skin?
Dry and dehydrated skin can feel much the same, but they lack different things. Dry skin is a skin type that produces too little oil (sebum). It needs emollients and occlusives to soften and protect – try our Ultra-Rich Cream, Instant Repair Balm or Vitamin Face Oil.
Dehydrated skin is a temporary condition where the skin lacks water – and any skin type can be dehydrated, even oily skin. It craves humectants, followed by a moisturizer that keeps the water in. Try our Intense Hydra Serum or Intense Hyaluronic Mask, followed by Daily Hydra Cream.
Read all about the difference in our blog post: Dry versus dehydrated skin.