Ointments are semi-solid, greasy preparations for application to the skin, rectum or nasal mucosa

Creams are semi-solid emulsions, that is mixtures of oil and water

• oil-in-water (O/W) creams
• water-in-oil (W/O) creams

Gels are semisolid system in which a liquid phase is constrained within a 3-D polymeric matrix (consisting of natural or synthetic gum) having a high degree of physical or chemical cross-linking.

These are free flowing very fine powders for external use.

A transdermal patch or skin patch is a medicated adhesive patch that is placed on the skin to deliver a specific dose of medication through the skin and into the bloodstream.

These are fluid preparations (aqueous) for external application without friction.