Onions contain powerful antioxidants and are anti-inflammatory, antibiotic, and antiviral. They are a great source of quercetin, one of my favorite anti-inflammatory compounds (and athletes need all the natural anti-inflammatories they can get). Quercetin can help relieve asthma and hay fever by blocking some of the inflammatory responses in the airways. Note: the strongest-tasting onions have superior properties.
Jonny Bowden, PhD, CNS, author of The 150 Healthiest Foods on Earth