Ointments are pharmaceutical preparations intended to be used topically on the skin. They are usually water-in-oil emulsions and sometimes contain a medicinal agent. There are different types of ointment bases that can used including oleaginous bases, absorption bases, water removable bases, and water soluble bases.

 Oleaginous bases are composed of long, water insoluble hydrocarbons that result in a waxy like substance. Examples include petrolatum and white petrolatum. Only small amounts of water soluble substances can be incorporated into these bases and solid substances can be incorporating using levigating agent. These bases can be difficult to wash off with water, can remain on the skin for long periods of time, and can protect and soften the skin. Often times an absorption base with a medicinal agent is incorporated into an oleaginous base.

 Absorption bases are used to create water-in-oil emulsions of the chosen substances. They consist of an oleaginous base along with an emulsifying agent which allows incorporation of more aqueous solution. Aqueous solutions can be incorporated into the absorption base, which can then be incorporated into an oleaginous base. Examples of absorption bases include lanolin and hydrophilic petrolatum.

 Water soluble bases as you could guess, are water soluble. For this reason the addition of too much of an aqueous solution can lead to softening, making the mixture have too much of a liquid characteristic. These bases are typically used for the incorporation of solid substances. The most common water soluble base is polyethylene glycol. Polyethylene glycol is available in polymers of varying molecular weights. PEG's with low molecular weights are clear liquids, and PEG's with higher molecular weights (over 600) are waxes or semisolids. Two PEG's of different molecular weights are often combined to achieve the desired viscosity, and the amounts of each used depend on the substance which is to be incorporated.

Water removable bases are oil-in-water emulsions, therefore they are easily washed from the skin, aqueous solutions can be added in higher amounts, and they can absorb oil secreted from the skin.

Other ingredients found within ointments are preservatives. These protect against the growth of bacteria or other microbes. Common preservatives used in ointments are methylparaben and propylparaben.