A lotion is a low- to medium-viscosity medicated or non-medicated topical preparation intended for application to unbroken skin. Most lotions are oil-in-water emulsions but water-in-oil lotions are also formulated. Lotions are usually applied to external skin with a clean cloth, cotton wool or gauze. The key components of a lotion emulsion are the aqueous and oily phases, an emulgent to prevent separation of these two phases, and, if used, the drug substance or substances. A wide variety of other ingredients such as fragrances, glycerol, dyes, preservatives, vitamins, proteins and stabilizing agents are commonly added to lotions.
It is not uncommon for the same drug ingredient to be formulated into a lotion, cream and ointment. Creams are the most convenient of the three but are inappropriate for application to regions of hairy skin such as the scalp, while a lotion is less viscous and may be readily applied to these areas. Lotions also have an advantage in that they may be spread thinly compared to a cream or ointment and may economically cover a large area of skin. Non-comedogenic lotions are recommended for use on acne prone skin.