Often when you look at the ingredients list for lotions, sodium hydroxide is listed way down on the bottom, and they quite commonly found (ex. Nivea).
So what exactly is such a strong base used for? When we made soap, we also used it. Just a recap of why we needed the strong base, the oils that we started off with to make the soap were fatty acids, which are quite hydrophobic. The NaOH makes these fatty acids into salts of that fatty acids. This is why a soap works – the Na+ end can dissolve in water and the carbon chain can dissolve in the oils, and this makes it possible to wash away the oil using water.
For lotion, the NaOH is used as a neutralizer in a very low concentration that would not cause sever burning. NaOH neutralizes the acidic fatty acids, like stearic acid which is another in credit, to make the carbon chains more friendly to our skin.
I had never noticed that. I’ll be looking for it now though!
I think that if I hadn’t made soap or read this post, I would have been very worried after seeing NaOH on the ingredients list of my lotion. Great biochemical breakdown of the mechanism!