Moisturisers can be broadly classified into three categories: 1. Occlusives form a barrier on the surface of the skin that water molecules cannot penetrate. In this way, they lock-in the water molecules that are already present inside the skin, thereby keeping the skin hydrated.
2. While occlusives form a barrier on the outermost layer, Reparatives actually penetrate the skin and fill the gaps between cells that are missing fatty layers of lipids.
3. Humectants help draw water to the skin. When applied, humectant molecules attract moisture from the environment and retain it inside the skin.