The terms 'moisturiser' (to add moisture) and 'emollient' (to soften) are interchangeable as they describe different effects of these agents on the skin.

Basically they have two actions:

• Occlusives which provide a layer of oil on the surface of the skin to slow water loss and thus increase the moisture content of the stratum corneum.
• Humectants which are substances introduced into the stratum corneum to increase its water holding capacity.

See also:

• smegma