Q. What is a sulfate free shampoo?
There is no official definition but broadly cosmetic companies class a shampoo as sulfate free if it does not contain
1. SLS or SLES (sodium lauryl sulfate and its gentler form sodium lauryl ether sulfate)
2. ALS or ALES (ammonium lauryl sulfate and its gentler form ammonium lauryl ether sulfate)
Q. Are sulfate free shampoos more gentle?
Many sulfate free shampoos have low irritation but not all of them do. You must always trust how your hair and scalp feel after the wash.
There is one particular ingredient in some sulfate free shampoos called olefin sulfonate which is actually comparable in irritation to SLS. Remember that SLS is one of the most effective surfactants and gets rid of oil very easily but as a result is also quite harsh on skin. One study on irritation produced a good relative comparison between shampoo surfactants (Journal of the Society of Cosmetic Chemists, pp125-139,1986). I have highlighted the ingredients according to how similar they are in terms of irritation in the table below
|Sulfate and Sulfate Free Shampoo Surfactants|
|Surfactant||Sulfate Free||Charge||%Skin Swelling (in 1hr)||Irritation Intensity|
|SLS||No||Anionic (-)||20-40% ||Severe in 1 day|
|Olefin Sulfonates ||Yes||Anionic |
|15-26%||Severe in 1 day|
|13-21%||Intense by day 4|
|11-17% ||Moderate by day 5|
|Sorbitol esters (polysorbate/tween 20)||Yes||Non-ionic |
|0.2-0.5% ||None expected |
From the table you can see that olefin sulfonate which some call a 'mild' surfactant is actually comparable to the most irritating surfactant SLS. Meanwhile SLES which is regarded as a 'harsh sulfate' is much gentler generally producing a moderate reaction if left on skin 5 days after washing.
There are other surfactants such as sorbitol esters used in sulfate free shampoos which are genuinely more gentle (more to come in a future post).
Q. Does your shampoo contain olefin sulfonate?
From the shampoos that you listed, the following do contain olefin sulfonate
1. Trader Joe's Tea Tree Tingle (C12-C14)*
2. Ion Inspired by Nature Shampoo (C14-C16)
3. Giovanni Teat Tree Triple Treat Shampoo (C12-C14)*
4. Giovanni 50:50 Balanced Hydrating Clarifying Shampoo (C14-C16)
5. Giovanni Smooth as Silk Deep Moisture Shampoo (C14-C16)
6. Kinky Curly Come Clean (C14-C16)
7. Organic Care Systems Power Build and Moisture Shampoo (C14-C16)
* - In the journal cited above, the C12-14 olefin sulfonate causes the greatest amount of irritation. (If you are wondering, C12 means that there are 12 carbon atoms, C16 means that there are 16 carbon atoms. In general making the surfactant larger i.e more carbon atoms usually reduces irritation)
Next up I will go through some more of the popular surfactants used in sulfate free shampoos and will highlight the ones which ARE not thought to irritate the skin.
Thank you to the commenters who asked specifically about olefin sulfonate in previous blogs and set up this series :)