OK… so, here it is. The Dish on Soap, if you will.
Bars of soap wash things off your skin. Nothing they put IN the soap is really going to stay on you and act as anything. It may leave you smelling a bit like the soap, because of the fragrance oils that will tend to stick and linger. Adding oatmeal is going to give the soap a scrape-y feel against your skin if you are one of those ‘use the bar straight on the body’ type of people. The oatmeal may also change slightly, the feel of the lather. As I mentioned, when oatmeal has water added to it, it creates this sort of slime. But because it is soap, it is going to be washed off down the drain and it does not impart any special healing or soothing properties that the soap wouldn’t have if it did not contain oatmeal. Gimmick, sure, but that is what fills the majority of our product choices, especially when it comes to something as mundane as soap.
I make soap. I make all sorts of soaps. There are differences in soap. You can vary how harsh or gentle the soap is and effect how well it lathers. Colour, fragrance, texture have less to do with how well a soap works and more to do with our psychology.
Commercially made soaps are made using a different process and with a wider range of chemicals. Liquid soaps, like shower gel, are generally not soap at all, but are made with foaming surfactants called sulfates, usually sodium laureth sulfate, or ammonia laureth sulfate. Most shampoos are sulfate based, too. Some bar soaps can contain real soap (saponified oils) as well as foaming surfacants and these bars are called sidnet bars.
These all have the same thing in common. They break the surface tention of the water, create lather, remove oil and dirt from what you are washing, dissolve it all in the water than flows down the drain.
I detest the marketing BS around cosmetics and soaps. People pick up my soaps and ask, what is this good for? I see it has such&such in it. I tell them, ‘It cleans your skin and smells nice.’
Yes, I make a goat milk soap with honey and oatmeal. The oatmeal feels nice and scrape-y on your skin and the honey smells good.
I would take into account the more active ingredients in the bar of soap first.