I noticed a warning on a box of kitchen foil saying it shouldn't be reused. I've been washing, drying, and reusing foil for years - should i stop? The warning appears for two reasons one more vital than the other. The practical problem is that, if you use foil to wrap or cover food during cooking, it may be weakened by the high temperatures inside the oven. More important, thought, is the hygiene issue. If you use foil to wrap or cover raw food, then use it to wrap or cover cooked food you risk transferring bacterial that could give you food poisoning. If you want to reuse foil, it essential to wash it thoroughly and dry it first, especially if its been used on raw meat, fish or eggs. If foil isn't cleaned and rinsed properly, problems could arise through the growth of food poisoning micro organisms that could contaminate food wrapped in the foil.