I have seen a few kinds of drugs being stored in aluminum foil, and aluminum is harmful to the human brain (some say it causes Alzheimer's disease). Does aluminum metal goes into the drugs it is containing? And is it generally harmful to people taking these drugs?
Well is it dangerous to store your food in tin foil? Oh wait I forgot thats what most people do... But I'm pretty sure if the drug is say DMT, and there is some lye left over in it, lye will react with tin foil so its not a good idea to store DMT or anything you extracted yourself that still may have lye.
I'm not sure if its harmful but I would personally avoid it. I prefer storing in plastic bags or in glass.
If you have lye in your DMT, you're not done extracting. But as a general rule, no, it's not much of a problem.