All these Shampoos use a chemical called SLS which is actually a floor cleaner. They are added in these products so as to produce more foam. Imagine what a floor cleaner can do to you hair and scalp. It will damage the very roots of your scalp.
Check out for SLS in toothpaste too!!! Use the ones which are free from this extremely harmful chemical. Type in 'SLS Free Shampoo' or 'SLS Free Toothpaste' in Google.com to get a list of companies selling safe products.(The Above Shampoos are Banned By Dubai Government too!!)