Remember that phrase “squeaky clean?” You can wash your hair with a shampoo that so thoroughly strips the oil away that your hair literally squeaks when you rub it. Not a molecule of oil is left to ease the friction. And it was considered a good thing.
Today we know that washing your skin and hair can do more harm than good. When you remove your own oil from the skin, you are breaking down the body’s primary line of defense against disease.
Think about it. If scrubbing your skin with soap were good for you, why would it feel tight, dry, and itchy afterwards? Why does it look red and irritated? Your body is reacting to a harmful process and trying to defend itself. The best hand soap would be one that removes dirt without removing the skin’s own oils.
Skin cleansers are formulated to remove dirt, sweat, sebum and oils from the epidermis. They do this through surface-active agents, or “surfactants” for short. Surfactants work by attaching themselves to the tiny particles of dirt and grime and dissolving them in water. They also play a role in the process of exfoliation.
Surfactants as chemical agents can be found in a variety of products like perfume, lotions, shampoos, and conditioners. They act as emulsifiers,wetting agents, foaming agents, detergents, and conditioners.
The surfactants found in skin cleansers are supposed to leave users with clean, glowing skin, but that doesn’t always happen. They can damage the stratum corneum, which is the outermost layer of the epidermis, resulting in after-wash tightness, dryness, damage to the integrity of the skin, redness, irritation, itching, and inflammation.
How Soaps Interact with the Stratum Corneum
To understand how surfactants irritate the skin, it’s necessary to understand how cleansers interact with the various components of the stratum corneum, the outermost layer of the epidermis. The stratum corneum consists of layers of dead keratinocytes(cells that produce a protein called keratin) that are constantly being pushed to the surface. When a layer of keratinocytes reaches the outermost layer of the stratum corneum, they’re called become corneocytes.
Corneocytes have lost their nuclei and cytoplasm. They become hard and dry. Soapsattach themselves to these proteins and restore water volume, causing them to swell up. The swelling permits cleansers to get deeper into the layers of the skin, where they potentially come into contact with nerve endings and the immune system, which leads to itching and irritation. After the water evaporates, the corneocytes become even drier than before, and that dryness can last for a long time. Soaps can reduce the skin’s natural ability to moisturize itself.
The Effects of Soaps on Lipids
The stratum corneum also contains oils that help skin stay moist. The precise effects of soaps on these lipids are not completely clear, but scientists inform us that surfactants can penetrate and disrupt the lipid bilayers, resulting in an increased permeability. Surfactants may even damage the basic structure of the fatty acids themselves, reducing the amount of lipids in the skin available for use.
Soaps and pH Levels
Surfactants come in two broadly divided classes: soap-based surfactants and detergent-based surfactants. (The detergent-based surfactants, being synthetic rather than derived from natural sources, are called “syndets.”) Soap-based cleaners usually have a pH (approximately 10) which makes them vastly more alkaline than syndets. (Syndets are usually neutral, around pH 7 or lower.)Soap’s higher alkalinity appears to be a major cause of skin irritation that comes with the use of surfactant cleansers. The precise way in which this irritation occurs is unclear.