Hello. I've been formulating my personal blush and cream powder since I'm allergic to most synthetic preservatives. Some friends asked me to make them some so I started to sell some batches. I don't use preservatives but somehow, I would like to improve the shelf life of the product. The following are the ingredients: grapeseed oil, shea butter, beeswax, kaolin clay, glycerin, iron oxide and titanium dioxide. What are the best natural preservatives that is oil- soluble and easy to use? I've read in an article that oil based products needed antioxidants to avoid rancidity but I believe I needed added natural preservatives. Any suggestions? Thank you.