SLES or sulfates are bad for skin but not so much for hair. Yes, I may sound controversial but I have the science to back my claim.
Sulfate-free shampoos are in trend but instead, we should be looking forward to sulfate free face washes and body washes.
Why? Firstly, because all the harmful effect of sulfates like its ability to disrupt the skin protein structure or cause contact dermatitis is far more visible on the skin than on hair. Actually, in most cases, sulfate-free shampoos are causing more frizziness on hair than traditional sulfate-free shampoos.
Let me explain the reason.
In general, sulfate-free shampoos have low cleaning efficiency so we have all the reason to believe that they will not strip off the natural moisture content of hair but along with that, they may not remove hair buildup as effectively as sulfates. So hair feels coarse.
Another issue with sulfate-free shampoos is slightly more technical but let me try to simplify. The problem is lower conditioner deposition on hair.
Ideally, our hair has an anionic (-) charge that attracts the cationic (+) conditioners. Conditioners make our hair smoother because they are cationic and our hair just loves them.
As most of the shampoos contain a small part of conditioners, the conditioners in the shampoo will get deposited on hair while other foaming cleansers and impurities get removed.
Here is a relevant finding I have.