We really do expect a lot from our facial cleansers, even though we are only using them for such a brief window of time. In the minute or so that we are washing our face, we expect facial cleansers to remove dirt, oil, grime, makeup, while at the same time retain moisture to our skin. This concept of "wash on, wash off" really illustrates the complicated dual role a skin cleanser is expected to fulfill.
How is a cleanser expected to remove certain things, such as dirt and makeup, completely from the face, yet at the same time remove selective amounts of oil from the face to avoid over drying? This is the complicated role skin scientists face when inventing facial cleansers. Somehow, they have to strike the correct balance between the following ingredients commonly found in cleansers:
These "surface acting agents" are a blend of water-loving and water-phobic components. Surfactants tend to form circular structures called micelles which are formed with water-phobic components protected in the center; in skin cleansers, these micelles surround dirt, oil and debris. But as surfactants lift away oil, they actually change the pH of skin. Normal skin pH is around 5.5. This slightly acidic environment, called the acid mantle, protects skin from bacteria. Stripping away this acid mantle dries skin and leaves it open to bacteria.
Therefore, scientists have to play with the mixture of surfactants in facial cleansers. They can keep the pH of the facial cleanser low, which is better for skin, by using negatively charged, or anionic, surfactants. One example is sodium lauryl sulfates (SLS). However, SLS is an irritant. To counter, cationic (positively charged) or amphoteric (both positive and negative charges) surfactants are added. However, the tradeoff is this brings the pH closer to basic (> 7)! Plus, too many cationic charge would tend to bind to negatively charged skin, meaning nothing gets removed and your cleanser is harder to wash off. Are you starting to understand why facial cleansers are so complicated?
These are intended to help hydrate skin, but most importantly, they do so by protecting the natural skin barrier. Ingredients such as fatty acids and lactic acid help bring the pH back down to a level of acidity. Emollients that are often used in facial cleansers include dimethicone and cetyl alcohol. Humectants such as glycerin and panthenol are added since they have high water-binding potential.
These are included in most creamy, milky facial cleansers. Example ingredients include stearic acid, silica and carbomer.
Other ingredients are water, of course. Sometimes, preservatives are added to facial cleansers to help keep them free from bacteria. These include the parabens that are a subject of many debates on safety. Fragrance and dyes may also be added for pleasing color and odor.
Facial cleansers can come in a bar, liquid, cream or gel. The type you use depends on your personal preference. Some say a bar soap tends to not attract much oils, so they may not be good for oily skin. However, there are glycerin soaps (clear soap) that are actually quite good for oily skin. A cream is thought best for dry skin. Gel cleansers are recommended for oily skin.
There's no "magic" combination to facial cleansers. Most times, you have to try them to see if they are too irritating or too drying, or even too greasy, for your skin type. In general you should stick with cleansers that have a low pH (close to skin). Remember also that skin type changes with hormonal fluctuations, seasons and age, so you might need to use more than one cleanser. Whichever you choose, take some time to reflect on how complicated your cleanser is- then thank your cleanser for how well it works to clean your face!