Self-made lipstick is mainly composed of oil, so it is suggested to add some tea polyphenols or VE to resist oxidation. If the preservative must be selected from food grade, try potassium sorbate. Generally, the proportion of food added is 0.03%-0.05%, which can take effect, but potassium sorbate seems insoluble in oil, so it is necessary to dissolve potassium sorbate with glycerol first. So I recommend a cosmetic preservative. I saw in a paper that the combination of ethylhexyl glycerol and phenoxyethanol 1: 9, with 0.5% added, can be a good preservative.