I want to start selling a body butter with my current candle line, but I have recently been reading that I should add a preservative to the recipe. It only contains Shea butter, soy oil, sweet almond oil, cornstarch, and FO. Since it does not have water and if I put a 6 month expiration date do 'I really have to add it? I would rather be able to market it preservative free. Any advice would be helpful.Thanks.