HOME > Chowhound > General Topics >


Leftover Onions Poisonous?

I received an email from a relative (a forward of a forward) stating that onions attract and grow bacteria very quickly and that because of this, slicing an onion then consuming the leftovers a few days later (even if its been covered and refrigerated) can be harmful and make you ill due to how quickly they become contaminated.

I often only use half an onion and store the rest wrapped in plastic wrap in the fridge until I use it a few days later.

Is this claim accurate, should we not use onions long after they have been cut?

  1. Click to Upload a photo (10 MB limit)
      1. re: travelmad478

        That's a new one to me. Then again, my food safety practices should have killed me a dozen or more times by now.

        Not everyone seems to agree: http://www.chemistkitchen.blogspot.co...

      2. In my experience over the past few decades, when I receive a forwarded email, it's likely not worth the time to read. I would guess no, it's not accurate.

        1. How long is "not long after they're cut"? Hours? Days? Weeks? I can attest to using onions a few days after cutting has no ill effects, although the surfaces can dry out and look a bit grotty.

          1. Were it true, I'd have died in my thirties. 71 now and still saving and using half-onions …

            1. I don't eat much raw onion, and when I do it is unlikely to come from the onion I saved which has dried out a bit. That half onion gets cooked.

              2 Replies
              1. re: Steve

                Oh, I'd never use a leftover onion raw. Gotta have maximum moisture to use that way, but dried out a little cooks pretty well.

                1. re: Will Owen

                  As mentioned above, it must be a miracle I've made it this far, because I'm pretty casual about this kind of thing...but I've cut an onion in half and used the second half weeks later about, oh, a million times in my life. Still here.

              2. Storing onions more than a couple of hours will produce stinky onions. Terrible taste if using raw.

                If you are cooking them it's not so noticeable. I don't like storing onions at all but if you do, I would say one day max, more than that...you are eating skunk onions.

                3 Replies
                1. re: cajundave

                  That's not my experience. Putting an onion in the fridge suppresses its odor.

                  1. re: paulj

                    I sometimes simply slice off the old surface of that half-onion and carry on.

                    1. re: huiray

                      Not my experience either. I often have a chunk of sweet onion stored in a ziplock bag in my veggie drawer for eating raw. Still tastes good days later. If the cut side gets dried out, I cut it off and add to the stock bag in the freezer.

                2. Just wondering, does this relative also throw out any cooked food that has been left out at room temperature for more than a couple of hours?

                  3 Replies
                  1. re: huiray

                    Onions are really high in microbe-suppressing sulphur compounds. Together with garlic, they're probably about the least likely food to make you sick.

                    1. re: pippimac

                      Unless one is allergic to them or have a chemical sensitivity to them. :-)
                      [But then, I think you meant to point out their chemical constituents to the OP, not to me]

                      But I was wondering what the food handling and storage tendencies were, in general, of this relative of the OP who sent him/her that email - whether that person was of the "throw everything out that doesn't go into the fridge within seconds of being cooked" school.

                      1. re: huiray

                        Not certain of how my relative handles food at home, but she forwards a lot of random emails, some contain true and interesting facts others seem like BS ... I was looking for some input on the validity of the onion claim (which I got, thank you!).
                        For my purposes, seems like I will only eat fresh cut raw and will cook if been stored in the fridge for less than a week.

                        Or I could stick to buying pearl or boiler onions, no leftovers!

                  2. One of my favorite onion quotes is rooted in American history. It goes like this. In 1864, General Ulysses S. Grant declared in an advisory to the federal government, “I will not move my army without onions!”

                    Likewise, General Robert E. Lee complained the Confederate congress was unable “to do anything except eat peanuts and chew tobacco, while my army is starving….”

                    Fortunately for Grant and the troops, his demand was met. Immediately, Grant was sent three traincar-loads of the flavorful bulbs which were appreciated by soldiers for both their flavor and antiseptic properties when used to treat powder burns.

                    1. My brother went through a period of vegetable experimentation. One of the most daring was when he bought a bag of onions and then kept it under the kitchen counter, unrefrigerated, for 8 months. The results were a marvel to behold. We all know that elderly onions can sprout. Sane people throw them out at that point but not my brother. No, no, he just left them there. In time, the onions did more than sprout. They grew arms and legs and even developed a rudimentary intelligence. At night I could hear them behind the closed cabinet door, talking to themselves and moving around. God knows what they were planning.

                      Finally I couldn't stand it any more. I put on gloves and cleaned them out using a shovel. I would have used a flame thrower if one had been handy.

                      1. I saw this on Facebook or MSN yesterday...I said what? People believe anything these days. They must need onion sales, most junk like this is profit $$$ driven. :)

                        1 Reply
                        1. re: JannieSue

                          It all started with a Blogger trying to drum up attention. It worked/works