Caustic Soda or Lye or Soduim Hydroxide is a highly toxic chemical. There is no two ways about that.
From personal experience, I was using the granules mixed with water to unblock the drains. I accidentally dropped TWO drops of it on my leg and it started burning through my flesh before I could get my leg under the tap to rinse it off. Over a year later, and the two marks are still on my leg, not healed properly.
I found this really interesting bit about it on Wikipedia: “sodium hydroxide is used to digest tissues, such as in a process that was used with farm animals at one time. This process involved placing a carcass into a sealed chamber, then adding a mixture of sodium hydroxide and water (which breaks the chemical bonds that keep the flesh intact). This eventually turns the body into a liquid with coffee-like appearance, and the only solid that remains are bone hulls, which could be crushed between one’s fingertips.Sodium hydroxide is frequently used in the process of decomposing roadkill dumped in landfills by animal disposal contractors. Due to its low cost and availability, it has been used to dispose of corpses by criminals. Italian serial killer Leonarda Cianciulli used this chemical to turn dead bodies into soap. In Mexico, a man who worked for drug cartels admitted disposing over 300 bodies with it.”
If you recall some of the science experiments you may have done in high school, when you combine an acid with an alkaline you get a neutral result. And so, in soap making, when you mix the caustic soda (acid) with fat or oil (alkaline), you get a neutral result. Actually, what you end up with is glycerine which gives the soap soothing properties.
Nowdays, with most commercially produced soaps, glycerin (the byproduct of mixing lye with oils or fats) is removed from the actual soap and used for other products. This is a real shame because glycerin has soothing properties and is excellent for dry skin.
There is also just one more thing to mention. There are three types of lye: Diaphragm Cell (uses Asbestos), Electrolysis (uses Mercury) or Membrane (membrane). The membrane process seems to have the least environmental impact so if you can, inquire about that from the place you purchase your soap.
For example, they have an option to list ingredients BEFORE the process of saponification which would look like: olive oil, water, sodium hydroxide (caustic soda/lye) OR they can choose to list the ingredients AFTER the process of saponification which would look like this: sodium olivate. So, the same ingredients but before and after a chemical reaction they have different names.
I have covered misconceptions before, like “citric acid” and we all go “oh,noooo” but if “lemon juice” is used instead, we all go “oh that’s fine”. In this case we still go “caustic soda, oh nooo” but we need to understand that after being mixed with the alkaline fats or oils, it becomes neutralized and it’s caustic soda no more.
So. Try and avoid commercially produced soaps as much as you can, and go the handmade soaps. Still, always make sure you check out those ingredients just in case something is hiding in there, and if you are able to, ask the soap maker if they use the MEMBRANE lye.