What are emulsions

An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable). Emulsions are part of a more general class of two-phase systems of matter called colloids. Emulsions should be used when both phases, dispersed and continuous, are liquids. In an emulsion, one liquid (the dispersed phase) is dispersed in the other (the continuous phase). Two liquids can form different types of emulsions. As an example, oil and water can form, first, an oil-in-water emulsion, wherein the oil is the dispersed phase, and water is the dispersion medium. Second, they can form a water-in-oil emulsion, wherein water is the dispersed phase and oil is the external phase.
In pharmaceutics, hairstyling, personal hygiene, and cosmetics, emulsions are frequently used. These emulsions may be called creams, ointments, liniments (balms), pastes, films, or liquids, depending mostly on their oil-to-water ratios, other additives, and their intended route of administration. The topical dosage forms, may be used on the surface of the skin, trans dermally, ophthalmically, rectally, or vaginally. A highly liquid emulsion may also be used orally, or may be injected in some cases. Popular medications occurring in emulsion form include calamine lotion, cod liver oil, cortisol cream etc. Micro emulsions are used to deliver vaccines and kill microbes
An emulsifier (also known as an "emulgent") is a substance that stabilizes an emulsion by increasing its kinetic stability. Many different emulsifiers are used in pharmacy to prepare emulsions such as creams and lotions. Common examples include emulsifying wax, cetearyl alcohol, sodium laurate, liquid paraffin,  polysorbate 20, and ceteareth 20.