The onion has been eaten for hundreds and even thousands of year. However, due to its pungent smell, the onion was thought of as a low class diet. Today, the onion is eaten by everyone, regardless of wealth or power. It adds flavor to bland meals and gives them a unique taste.

The onion dates back to 3500 B.C. It may have been growing wild in every continent but some people believe that the onion originated in Asia. Since the onion is a food that did not spoil during the winter, it was grown by the people in history. In Egypt, the onion was worshipped because they believed that "its spherical shape and concentric rings symbolized eternity." In fact, the onion was so important, Egyptian artists sculpted in gold. The onion was also popular in ancient Greece. Greek athletes would eat a large amount of onions to "'lighten the balance of blood.'" After the Romans conquered Greece, the onion became popular with the Roman culture just like it was for the Egyptians and Greeks. According to Magic Valley Growers, the Roman gladiators would rub onion juice on their bodies to make their muscles firmer. As time moved on, onions were started to be used as medicine during the Middle Ages to "alleviate headaches, snakebites, and even hair loss."

Currently, onions are eaten regularly everywhere in the world. From the National Cancer Institute, onions are said to prevent cancer and lower cholesterol.

Reference
http://magicvalleygrowers.com/history.html.