I don't own a damascus blade, but I do have carbon steel kitchen knives. I'm not worried about darkening the patina because I don't have a design to deal with, but I wipe them down with food grade mineral oil every once in a while just to keep them from getting pitted. Has anyone with a damascus blade tried this? You don't actually leave much oil on the knife, and I've never had an issue with detecting it in/on my food. Is that why you don't want to use it?
Also, if you want to buy food grade mineral oil, it can be found in some cooking supply stores but I find it's usually cheaper in the drug store. (it's a laxative) Some people use baby oil, but I trust the USP grade stuff to not have additives or fillers. (USP grade is US Pharmacopia, it means that a substance is fit for human consumption or use in food or drug manufacturing, no toxic fillers)