Due to their anhydrous nature ointments do not require any preservatives. They have the advantages of being more moisturizing, more occlusive than creams and form a protective film over the skin. The occlusive effect tends to prolong and enhance drug penetration but they are messy. Because of their marked occlusive effect, ointments are not suitable for acute weeping, crusting skin conditions, particularly in intertriginous areas. Today, there are ointments that possess both hydrophilic and lipophilic properties so that they become water soluble and can be washed off readily.
Ointments are very useful particularly for chronic, dry skin lesions.
Ointments should be diluted to the required strength with the suitable diluent in the relevant entry. The material making up the container should be resistant to absorption or diffusion of its contents. Pastes Are stiff preparations containing a high proportion of finely powdered solids such as zinc oxide and starch. They are less occlusive than ointments and can be used in subacute, lichenified, or excoriated skin conditions. Due to their stiff nature, pastes can be applied accurately to a particular lesion such as chronic eczema and psoriasis, and are therefore useful for the local application of irritating drugs.