How to Know If an Onion Has Gone Bad

The other night I went digging through the bottom of my onion basket and pulled one out that felt wrong before I even looked at it. Soft on one side, a little damp, the kind of thing that had clearly been hiding down there a while. That squishy spot is usually the first clue an onion is bad. The good news is you can catch almost all of it with three quick senses: look, feel, and smell. Once you know what you’re checking for, it takes a couple of seconds.

What a Bad Onion Looks Like

Start with your eyes. A healthy onion looks even and firm with clean papery skin. A spoiling one shows dark or brown spots, sunken lesions, or fuzzy patches of mold in white or black. If you cut into it and the inner layers look unusually dark, wet, or mushy instead of crisp and pale, that’s decay working its way in.

Mushy discoloration once the onion is open is a clear no. So is any visible fuzz. What throws people is the outer skin. Brown, dry, flaky papery layers on the outside are normal and not spoilage on their own. Peel a layer or two off and check the flesh underneath. If it’s firm and bright under there, the browning was just the wrapper doing its job.

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How a Bad Onion Feels and Smells

Feel is where my basket onion gave itself away. Onions should be hard. Press one and it should barely give. Soft, mushy, or slimy means moisture has gotten in and the flesh is breaking down. Wet spots or any liquid leaking out are bad signs too, since onions are supposed to be dry to the touch.

Then there’s the nose. A raw onion smells sharp and a little pungent, and that’s fine. What you don’t want is sour, musty, or straight-up rotten. In my experience the smell test is the tiebreaker. If an onion feels a bit soft and also smells off, that combination is the strongest signal you’ve got a spoiled onion on your hands. Toss it.