Emulsifiers are additives that can disperse fats or fatty oils in water in the form of tiny droplets with the specific feature that the droplets do not separate again. Emulsifiers are used in cosmetic creams, medical ointments, food, cleaners and shoe polishes.
Emulsifiers are the interfaces between water and oil droplets. The reason behind is that emulsifiers consist of two parts:
- One portion of the emulsifier is soluble in water and insoluble in fat; it extends into water.
- The other portion is fat-soluble and insoluble in water; it extends into the oil droplets.
We speak of an oil-in-water-emulsion (O/W) when the oils are dispersed in water as described and, vice versa, of a water-in-oil-emulsion (W/O) when the water droplets are dispersed in oil.
When emulsifiers are mixed with water (without oils) they generally stack together to form spherical bodies. In the process, the water-insoluble portions orientate themselves towards the interior of the globules and the water-soluble portions on the outside towards the water.
The spherical bodies are called micelles. Micelle water is water that contains emulsifiers.
Micelles can absorb fats and oils. Due to this specific feature they can be used to cleanse the skin. Fats are emulsified and eliminated from the skin. The emulsifiers used in cleansing compounds are called tensides. The abbreviation WAS (wash-active substance) on the label informs on the tenside content.
Emulsifiers are potential irritants; in particular if they are non-biodegradable and affect the skin barrier. In this case they wash out barrier substances when the skin is cleaned. This effect also is observed with cosmetic creams that contain emulsifiers. Emulsifiers based on polyethylene glycols (PEG) tend to form radicals when they are exposed to UV radiation.
H. Lautenschläger, Emulsifiers enable mixtures, Kosmetische Praxis 2004 (3), 8-10
H. Lautenschläger, Emulsifiers - looking for alternatives, Kosmetik International 2000 (12), 112-113
H. Lautenschläger, From soap to high-tech emulsifiers, Beauty Forum 2010 (11), 20-22
Dr. Hans Lautenschläger