Hydration is two jobs, not one: getting water into the upper layers of skin, and stopping it leaving. Products that do only the first evaporate; products that do only the second seal in nothing.

The two ingredient roles

Humectants attract and bind water. Glycerin and hyaluronic acid are the familiar examples. They pull moisture toward the skin's surface.

Occlusives and emollients form a layer that slows water loss and smooths the surface. Oils, butters, silicones.

A good moisturiser contains both. This is why "a serum instead of a cream" often disappoints on dry skin — the humectant does its job and then the water leaves, because nothing held it.

The damp-skin rule

The single most effective habit in this article: apply moisturiser within a minute of cleansing, while skin is still slightly damp.

Humectants bind whatever water is available. On damp skin that means the water on the surface. On bone-dry skin in a dry room, they can draw moisture from deeper layers instead — which is the opposite of the goal.

Pat the face, do not dry it fully, then moisturise.

What about drinking water

It matters, and less than people assume. Skin is one of the last places the body sends spare water, so severe dehydration shows in your skin — but going from adequate to abundant intake does very little.

Drink enough. Do not expect it to replace a moisturiser.

The environmental half

Often larger than the product half:

  • Central heating is the biggest indoor cause of winter dehydration. A humidifier in the bedroom frequently outperforms a new cream
  • Air conditioning does the same in summer
  • Long hot showers strip lipids
  • Wind and cold accelerate water loss

Layering, if you want to

Thinnest to thickest: toner or essence → serum → cream. Each layer within a minute of the last, while skin is still damp.

More layers is not better. Two well-chosen products beat five.

By skin type

  • Oily — light gel-cream, twice daily. Skipping it makes oiliness worse
  • Dry — richer cream, especially at night
  • Combination — light everywhere, more on the cheeks
  • Dehydrated — fix the cause first (usually over-cleansing), then hydrate

For cream textures, see the face cream guide.