Non toxic knife oil that is safe for food prep. Your choices are mineral oil, baby oil, gelled baby oil, or vegetable/olive oil.
The mineral oil and baby oil which is mineral oil with fragrance added is not meant to be ingested but is approved for topical use.
It's not really toxic unless you drink a shot or two and even then it will act like a laxative.
Any oil that you cook with, vegetable oils are fine but the longer they sit the more they oxidize and will have a foul taste and sour smell.
What ever oil you use, it would be advisable for you to wipe the blade down before and after use. If you are packing your lunch, spray a 3" cotton rag/tee shirt square etc with non stick cooking spray, put it in a zip lock bag. After you eat, clean and wipe down your blade.