Onions.

Onions are an excellent antioxidant, and they contain anti-allergy, antiviral and antihistamine properties.
Sulfur compounds in onions help to detoxify the body.
Onions aid in cellular repair.
Onions are a rich source of quercetin, a potent antioxidant.
To obtain the maximum nutritional benefits, onions should be eaten raw or lightly steamed.