While it doesn't hurt to wash onions before cooking, it's not necessary. Not only do onions have a protective outer casing, but they're also listed as one of the cleanest veggies in terms of pesticide exposure. ... Also, if your onions have clear signs of dirt, you should wash them before cutting.

Does onion need to be washed?

Onions to be used in any raw preparation should be calmed by a cool rinse and patted dry before using. When we tested our Tomato-Serrano Salsa, we found that rinsing the minced onion removed the pungent bite that might overpower the subtle sweetness and bright acidity of fresh tomato and lime.

How do you wash onions before storing them?

Place the green onions in a bucket of cold water to soak off excess dirt. Remove any remaining dirt by rinsing the onions under cold running water, pulling apart the leaves to allow the water to run through.