Moisturiser ingredients can be placed into 3 groups:
- Occlusive moisturising ingredients
The terms moisturiser and emollient are practically synonymous.
Occlusive moisturising ingredients work by trapping water in the skin. They act almost like a layer of plastic on top of the skin. Petrolatum is an example of an occlusive moisturiser.
Humectants work by sucking water into the skin. They act like a sponge inside the epidermis. Urea is an example of a humectant.
Oils work by replacing the lost natural oils in the epidermis. If the epidermal cells are the bricks of the epidermis, the oils will be the mortar. Cholesterol, fatty acids and ceramides are examples of natural skin oils.
A good moisturiser should contain ingredients from all three categories.