Dear Tonya: Why is it that some products formulated with "gentle" surfactants and marketed as natural or sulfate-free actually seem to be more drying and damaging to my hair? I thought these products were supposed to be more gentle and kind to my fragile curls.
A: This question pops up frequently, and I have asked it myself when trying out new products without having really scrutinized the ingredients list. (Yes, even the CurlChemist sometimes buys things without much regard for the ingredients list, simply because the products look nice, smell nice, or have good promises on the package). Several factors are at play here.
Concentration of Cleansing Agent
It is possible that some of these sulfate-free shampoos contain very high percentages of surfactant, resulting in a product that is more effective at removing fatty acids and dirt from the scalp and hair. This can be disastrous for hair that is already fragile and that struggles with being too dry already. Unfortunately, it is not possible to determine this information by reading the ingredients list, as the labeling requirement is simply that the ingredients are listed in order of concentration—typically highest to lowest. Thus, the first surfactant on the list could be in the formula at 10%, 20%, or even 30% (or anything in between), and it would not be evident to the consumer.
Lack of gentle co-surfactants
Many products formulated with some of the stronger surfactants contain additional detergents called co-surfactants. These are typically materials such as cocamidopropyl betaine, fatty alcohols, and mild cationic surfactants. The mixture of these various surfactants act to diminish both the potential irritancy of the product and the oil stripping capability. The micelles formed in such mixed surfactant systems exhibit different physical and kinetic behaviors than those comprised of a single surfactant. The result is typically a milder formulation. Some of the products advertised as more pure or more gentle actually leave this important step out of their formulation.
Lack of fats/oils/conditioning agents
Good-quality cleansing products include moisturizing agents in their formulation that help to redeposit some oils onto the surface of the hair to prevent excessive drying from the washing process. Again, some of the simpler products that claim to be gentle may be missing this important component of the formulation.
Human hair has a natural pH (called its isoelectric point) of around 4.5. Any product with a pH higher than that is therefore alkaline with respect to the hair, which makes it inherently more drying and damaging to the cuticle and the fatty acid layers on the surface of and within the cuticle. Many of the surfactants used for shampoos are stable only in a narrow pH range—often between 5-7. For this reason, the majority of shampoos are formulated to be around 6 on the pH scale. It is possible to obtain a gentler product by formulating it to have a pH of around 4.5 - 5.5, closer to the natural state of hair (pH = 4-4.5), but it must contain surfactants that are stable at that pH. These types of products will usually have citric acid or some other mild acid near the end of the ingredients list. You can order pH test strips if you want to check out some of the products in your bathroom yourself.
Some ingredients to look for when choosing a gentle or mild shampoo for your hair are:
- cocamidopropyl betaine and other betaine surfactants
- carboxylate surfactants
- sodium lauroyl lactylate, sodium caproyl lactylate
- sodium laurylglucosides hydroxypropyl sulfonate
- cocoglucosides hydroxypropyltrimonium chloride
- sodium cocoamphopropionate, sodium cocoyl isethionate, disodium laureth sulfosuccinate
- nonionic polymeric surfactants
- lauryl-glucoside sodium maleate crosspolymer, lauryl-glucoside sodium succinate crosspolymer, decyl-glucoside sodium maleate crosspolymer
In conclusion, it is important to remember that a shampoo is comprised of a number of ingredients meant to work together to achieve the goal of clean, manageable hair. The label does not reveal the entire story, but it can allow us to glean important clues as to whether a particular shampoo might be more or less inclined to strip our curls of too much moisture. A single ingredient (or lack thereof) is not sufficient to predict the performance of a particular product, and the list of mild surfactants is in no way comprehensive. It is important to consider the total ingredient list, where one should be looking for not only certain types of cleansing agents, but also various combinations of different types of surfactants, polymers, oils, and other conditioning agents (humectants, vitamins, etc.). Physical properties such as pH also play a role in the mildness of a shampoo.
So, when selecting a new product, consider all of these factors in your evaluation. As always, if you find something that works for you and that you like, consider that to be your most valuable bit of scientific data and keep using it, even if the "science" says it might be harmful. In contrast, if the "science" says that a product should be good and gentle (i.e. "sulfate-free"), but your hair responds poorly to it, listen to that information as well! Only you know what you want most from your curls.