Microemulsions

What Are Microemulsions?

A microemulsion is a system composed of water, oil and an amphiphile (surfactant) that forms a single, optically isotropic system. Depending on the formulation, the internal phase can consist of oil droplets dispersed in water or water droplets dispersed in oil.

The dispersed structures typically have diameters of approximately 10–200 nm, which allows microemulsions to appear optically clear or translucent. They can occur as liquid or gel-like systems.

Properties of Microemulsions

Microemulsions are generally more stable than conventional emulsions and can be used to incorporate or solubilise active substances. Their small droplet size can also support improved skin penetration and permeation of certain ingredients.

They are commonly described as ternary systems consisting of water, a lipid phase and a surfactant mixture in a specific ratio.

Surfactants and Skin Tolerance

A potential disadvantage of microemulsions is their relatively high surfactant concentration, which may increase the risk of skin irritation or sensitisation. Modern formulations may use alkyl polyglycosides, which are generally considered milder than conventional polyoxyethylene-based nonionic surfactants.

References

Handbook of Cosmetic Science and Technology – André O. Barel, Marc Paye, Howard I. Maibach.