I have had several friends & customers mention that they are allergic to nuts and wonder if I offer nut-free soaps. Many of those individuals are specifically allergic to tree nuts like almonds or hazelnuts, but seem to do okay with coconut oil. That is fortunate, because coconut oil is in almost EVERY bar that I make. (Check out my bars for sensitive skin here).
The reason coconut oil is so common is soap is that it helps contribute cleansing properties to a bar (too gentle and the soap won't actually help you remove grime as easily), and it helps harden the bar (so that it doesn't soften up and disintegrate so easily in the shower... though remember - try to let your bars dry between uses, hopefully on a draining shelf or dish!). It is also economical in price.
Recently I met someone who is also allergic to coconut oil, so this presented a new challenge. In researching oils that would replace the qualities of coconut, only a few options presented themselves: palm oil (there is environmental concern about how this is harvested so I don't generally use it); tallow (though some people don't like the idea of beef fat in their soap); or babassu oil, which comes from the seeds of the babassu palm in the Amazon. A fourth option is a traditional Castile Soap bar made of 100% olive oil, which I also plan to experiment with.
My final recipe for this experiment uses a blend of Babassu, Castor, Olive and Avocado oils, along with Cocoa & Shea Butters. It is scented with Lavender & Lemongrass. I can't wait to try it!