By Shannon R., SELF magazine
The history of soap making dates back to around 2800 BC so I think it's fair to say that soap has been around a long time! Soap served many purposes-- bathing, washing hair, laundry. The market for soaps has diminished due to the creation of synthetic surfactants (found in almost all cleansing products) but it does make you wonder, is soap an effective way to wash your hair?
Related: 21 Good-For-You Snacks
What is soap?
Soaps are made by reacting fatty acids with a base (like sodium hydroxide which has a high pH) in a process called saponification. Ancients used animal fat (tallow) as as starting material but modern soap making uses vegetable or plant oils like coconut, palm or olive.
See more: The Healthiest Cities for Women
What is a synthetic surfactant?
This type of detergent is created by combining a fatty alcohol with an acid. Fatty alcohols can be distilled from petroleum or derived from natural oils (coconut oil is commonly used).
What does this mean for my hair?
Okay, enough of the chemistry lingo-- here is the dope on soap. The primary problem with soap is that there can be a chemical reaction (particularly if you have hard water) that forms an insoluble material (meaning it can't be dissolved) in water. This is what causes the "soap scum" you see lining bathtubs and sinks. This same sort of "film" can form on your hair leaving hair feeling dirty and weighed down. Synthetic detergents do not react like this so this "film" is not an issue.
Another issue with soap is that they are generally solid at room temperature and are limited in the number of ingredients you can add to them. Synthetic detergents are liquids and give cosmetic chemists much more flexibility when formulating with them. Overall, synthetic detergents are clean rinsing, don't leave residue and can be formulated to easily include conditioning agents that leave hair feeling soft, smooth and clean.
See more: Foods That Fight Cellulite
You can certainly wash your hair with soap, but if you are used to liquid shampoos you likely won't be happy with the results. Soap can leave hair feeling dry and waxy and won't provide many of the benefits of liquid detergents. However, if your only goal is clean hair (or you are trying to limit carry-on travel items!) then soap may be an option. Happy sudsing!