Human hair has a tendency to accumulate dirt, skin particles and environmental contaminants due to the protective oils secreted by the skin of the scalp. This oil also makes it difficult or impossible to cleanse hair reliably with water alone. Until relatively recently, the process of washing hair was no different from washing skin. People used the same simple soaps they used to remove dirt and oil from their skin in their hair, and they did so infrequently. This was partly because the film from the soap left the hair irritated and unhealthy looking. Commercially made shampoo has only been available since the early 20th century, and it wasn't until the 1970s that most people began washing their hair on a daily basis. Now a wide variety of hair cleansing products exist that claim to provide a myriad of benefits to hair shafts beyond simple cleansing. Aveeno's Nourish shampoos purportedly do so in part because of their ingredients.
Ammonium Lauryl Sulfate
This is an anionic surfactant found primarily in shampoos and body washes as a foaming agent. A surfactant acts by disrupting water's hydrogen bonding. In water, ammonium lauryl sulfate separates into positively and negatively charged ions. The negatively charged ions arrange themselves into a sphere, and the water molecules in the solution bind to the outer surface of the sphere instead of to one another. This enables the water to more readily penetrate things like hair, carrying the cleansing materials in the shampoo with it and more easily breaking up dirt and oil.
PDMS has some unique chemical properties that have led to it being used in a wide range of products, from silly putty to lubricants to hair conditioner. It will act similarly to a very slow-flowing honey if left in one place long enough but will act like a rubbery solid over short time periods. As a conditioner, it coats the hair shafts and protects them from damage, leaving hair shiny and slippery.
Cetyl alcohol was originally derived from sperm whale oil, though today it is primarily synthesized from vegetable oils. It acts as a surfactant, as described above, and also as an emulsifier and thickening agent. An emulsion is a mixture of two unblendable liquids, such as oil and water. An emulsifier facilitates the blending of these two liquids by stabilizing the resultant mixture. In this way, cetyl alcohol helps the water, soap and other ingredients in the shampoo blend properly.
Mauritia Flexuosa Fruit Oil
Mauritia Flexuosa, or the Moriche palm, is a palm tree that grows near swamps in South America. The fruit is used locally to produce various edible products. The orange-reddish oil extracted from the fruit has been shown to filter some cancer-causing ultraviolet rays and, although UV-blocking shampoos have not been shown to contain sufficient quantities of such chemicals to properly protect hair from UV damage, this is the reason that the ingredient is added to many cosmetic products.
This is another surfactant intended to facilitate the penetration of soaps into the hair shaft. However, unlike ammonium lauryl sulfate's positive and negative ions, cocamidopropyl betaine is zwitterionic. A zwitterion is a molecule that possesses both positively and negatively charged atoms that cancel each other out, leaving the molecule as a whole neutral. The benefit is that a solution with too many negatively charged ions might be irritating to the skin.
- Househould Products Database: Ammonium Lauryl Sulfate
- Merck Index, 11th Edition; Susan Budavari; 1989
- "Handbook of Food, Drug and Cosmetic Excipients"; Susan C. Smolinske; 1992