Chemicals in facial cleansing products that propel the cleansing ability are surfactants. Surfactants are special class of chemicals that have unique chemical structures of hydrophobic (oil binding) and hydrophilic (water binding) portions on the same molecule. Surfactant can bring oil into water and water into oil.
There are a lot of surfactants in the market, they can be broadly categorized into anionic surfactant (those with negative charge), cationic surfactant (those with positive charge), switterionic or amphiphilic surfactant (both negative and positive charge on the same molecule) and nonionic surfactant (no charge).
- Anionic surfactanta are the main washing surfactants used in the market. They have good oil removal capacity, therefore, can clean oily and dirty surface effectively. They are used in various applications including dish washing, laundry detergent, body wash and strong facial cleansers. All soaps are anionic surfactant.
- Cationic surfactants are not usually used for dirt removal. They are used in neutralizing negative surface charge generated by the anionic surfactant. Their popular applications include fabric softeners and hair conditioners.
- Amphoteric surfactant or zwitterionic surfactants are mild on skin. They are used in cleansers for face or baby skin.
- Nonionic surfactants have no charge. They produce less foam comparing to other groups of surfactants. They are ofter used in products that require mildness.
High concentration of surfactants can dissolve cell membrane and induce cell death. This is because cell membrane is composed of lipids. Therefore, the use of surfactant on skin should be done with care, e.g., always dilute cleanser with water first, never massage surfactants against skin for a long time, try to have short contact time of surfactant on skin, and always rinse well.
Sulfate, sulfonate surfactants and soaps
Soap is a powerful anionic surfactant. Looking for soap ingredient in ingredient list of cleanser formulations is a bit tricky. Usually they are written as names of oils used to make soap and sodium or potassium hydroxide. This is because soap is a product of saponification reaction between oils and these strong bases.
The main ingredients in dish washing agent are sulfated and sulfonated surfactants. Sulfated and sulfonated surfactants possess high fat solubilizing capability, thus can remove all oils and grease on dirty dishes. These surfactants also give good foaming property and can be rinsed out with water quickly. In contrast to dishes, cleaning facial skin should not be that powerful. Natural lipids in skin barrier should not be removed by our daily routine cleansing. As a result, cleansers with no soap, sulfated and sulfonated surfactants have become popular for sensitive skin. Nevertheless, soap, sulfated and sulfonated surfactants have much lower price than milder nonionic and amphoteric surfactants. Therefore, sulfate-free cleansers usually cost more than other cleansers.
Good sulfate free and soap free cleansers can remove dirt and secreted oils on skin surface without disrupting skin barrier. Using these milder cleansers can result in healthy skin barrier. Nevertheless, your cleansing action also play an important role. Never massage cleanser directly on your skin, dilute it with water first. Keep in mind that contact time between cleanser and skin should be short whereas water rinsing time should be generous.
Be careful of facial cleanser with positively charged surfactants
With effective cleansing action of cheap anionic surfactants, dry and tight skin can be felt. Some of the formulators solve this problem by adding cationic surfactants into the formulations! The result is the cleansers with skin surface conditioning from positively charge surfactant. Softer skin can be felt immediately after washing due to the neutralization of the negatively charge surfactants with the positively charge surfactants. The effect is the same as when your hair is rinsed with positively charge hair conditioning. The immediate feeling is excellent! Nevertheless, there will be much higher risk for long term skin irritation and skin problem. Positively charge surfactant can cause more skin irritation, therefore, people with sensitive skin and acne prone skin should absolutely avoid this type of cleanser. This is the same reason as why people with acne prone or sensitive skin should not have hair rinse touching their face.