I believe mineral oil is an unnatural oil as it is a product of the oil/petrol industry and so has a bad rap. As it is unnatural it is not absorbed by the skin. Because of this it creates a good barrier that can lock moisture, product (sun protection) and medication in under it (or wax above it). Baby oil is mineral oil. Having a shower and before towelling off covering yourself with baby oil will lock a lot of the water left on your skin, under the oil. Ingrown hair treatment creams are often oily.
As mineral oil creates a barrier it is good as a pre-wax oil (Perron Rigots Jasmine Oil is mineral oil as are many other brands I would imagine). I use plain mineral oil for my pre-wax
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People are very unlikely to be allergic to inert/dead products like mineral oil in comparison to natural products like almond, rape and peanut.