Every shampoo in the market whether it is a normal shampoo or one which claims to be sulfate-free always contain some kind of surfactant. Surfactants are added in the formulation for their cleaning property as they act like a detergent. Their main aim is to remove the dirt, excess sebum and oil from the hair. As we all know, curly hair are already moisture deprived so using the shampoo containing harsh surfactants may lead to the stripping off of natural oils and moisture from our hair that it badly needs.
How surfactants act as cleaning agents
A surfactant molecule consists of two parts. The tail part, which is hydrophobic (water fearing) is non-polar and the other part is head, which is hydrophilic and it is polar in nature. This dual nature gives them their cleaning property. At good concentrations in water, surfactant molecules group together to form three-dimensional structures known as “micelles”. These structures are clusters of molecules with an oily center made up of the non-polar tail, surrounded by a shell formed by the polar portion of the molecule. These micelles absorb oils from your skin, hair or clothes, and trap them inside until they are removed from the surface by rinsing with water.
Types of surfactants
Surfactants are classified based on polarity of their head part. A non-ionic surfactant has no charge groups in its head. If the head carries a negative charge, then it is anionic. If it has positive charge, then it is classified as cationic. If a surfactant contains a head with two oppositely charged groups, it is termed zwitterionic or amphoteric.
So, now we know a little bit about the chemistry of surfactants. The question remains, which surfactants are harsh to skin and hair and which ones are milder and hence do not strip off our hair and are less irritating to the skin.
Most of the shampoos that are available contains one of the below anionic surfactant as their primary surfactant.
Below mentioned sulfates are the harshest anionic surfactant that we should avoid in our products.
Sodium Lauryl Sulfate (or sodium dodecyl sulfate) known as SLS
Sodium Laureth Sulfate or (sodium lauryl ether sulfate) known as SLES
Ammonium Lauryl Sulfate
Ammonium Laureth Sulfate
Sodium Myristyl Sulfate
Sodium Myreth Sulfate
Sodium Coco or Cocoyl Sulfate
Sodium C14-16 Olefin Sulfonate
TEA Lauryl Sulfate
Sodium Alkylbenzene Sulfonate
Ammonium or Sodium Xylenesulfonate
Milder and more gentle anionic surfactant are
Sodium Cocyl Isethionate
Sodium Lauryl Sulfoacetate
Sodium Socoyl (or lauryl/lauroyl) Sarcosinate
Ethyl PEG-15 Cocamine Sulfate
Dioctyl Sodium Sulfosuccinate (Diethylhexyl Sodium Sulfosuccinate)
Sodium Lauryl Glucose Carboxylate
Sodium Methyl Cocoyl or Lauryl Taurate
Sodium Cocoyl Glycinate
Sodium lauroyl/cocoyl glutamate
As opposed to other classes of surfactants, these positively charged surfactants are used primarily in conditioners. This class of surfactants is well known as a conditioning agent. Our hair is negatively charged. The more the hair is damaged, the more negative charge it carries. So, these positive charged cationic surfactant bond to our negative charged hair and get adsorbed (not absorb) on the hair shaft and provide the conditioning effect.
Most common cationic surfactant are
Stearamidopropyl dimethylamine (lactate, citrate, propionate)
This type is more gentle than anionic surfactant but does not foam as good as anionic surfactants. These are generally combined with other anionic surfactants to create the milder shampoo.
Non-ionic surfactants are
Laureth- (10, 23, 4)
PEG-10 Sorbitan Laurate
Polysorbate- (20, 21, 40, 60, 61, 65, 80, 81)
Steareth- (2, 10, 15, 20)
Amphoteric (or zwitterionic) Surfactant
These surfactants provides mild cleansing and are added with other anionic surfactants to reduce the irritation caused by them. They help to boost the foam formation when combined with other surfactants. These surfactants can not be used alone in the products as these do not provides good cleansing properties so are always to be used as secondary surfactant.
Ampoteric surfactant are
Tips for buying milder shampoos
- Avoid using products that contains sulfates and sulfonates.
- Prefer products having non-ionic and amphoteric surfactants. These surfactants should be listed on the top of the ingredients list after water meaning higher concentration of these are used than any other anionic surfactants mentioned in the ingredients list.
- Look for products in which only milder anionic surfactants are used.
- Other conditioning ingredients (like polymers or quaternary agents. Will write a post on conditioning agents later) should be present in the ingredients list to offset the drying effect caused by the shampoo.