Occlusive

An occlusive is a moisturising ingredient that forms a thin protective layer on the skin surface to slow the evaporation of water. Well-known examples include petrolatum, mineral oil, beeswax, lanolin, and many plant butters and waxes.

Occlusives work by creating a physical barrier over the skin that reduces transepidermal water loss, the process by which moisture escapes from the skin into the air. By trapping water beneath this layer, they help keep the skin hydrated and are particularly effective when applied over damp skin or on top of a humectant. Petrolatum is often cited as one of the most effective occlusive agents.

Occlusives are especially valued for very dry, cracked, or compromised skin and in cold, dry, or windy conditions. They form the basis of the routine known as slugging, in which a thin occlusive layer is applied as the final nighttime step.

Because they seal the surface, heavier occlusives can feel greasy and may not suit those prone to congestion or breakouts, though lighter options exist. They are best used as the final step of a routine, over water-based and humectant products, so that the moisture they help retain is already present.