In cosmetics, an emulsifier includes any ingredient that helps keep unlike ingredients (such as oil and water) from separating in an emulsion. Examples of cosmetics ingredients that function as emulsifiers include polysorbates, laureth-4, and potassium cetyl sulfate.
Emulsifiers are widely used throughout the cosmetics industry and are the unsung heroes of many cosmetics formulas that blend and help to keep unlike ingredients together. There is also research showing they can help enhance the absorption of skincare ingredients and may be useful for prolonged topical delivery.
Reference for this information:
Percutaneous Penetration Enhancers Chemical Methods in Penetration Enhancement, 2015, pages 223-241