"Onions are cultivated and used around the world. As a foodstuff they are usually served cooked, as a vegetable or part of a prepared savoury dish, but can also be eaten raw or used to make pickles or chutneys. They are pungent when chopped and contain certain chemical substances which irritate the eyes. Consumption is believed to benefit health in that onions contain phenolics and flavonoids that have potential anti-inflammatory, anti-cholesterol, anticancer and antioxidant properties.
Common onions are normally available in three colours: yellow, red, and white. Yellow onions, also called brown onions, are full-flavoured and are the onions of choice for everyday use. Yellow onions turn a rich, dark brown when caramelized and give French onion soup its sweet flavour. The red onion is a good choice for fresh use when its colour livens up the dish. It is also used in grilling and char-broiling. White onions are the traditional onions that are used in classic Mexican cuisine. They have a golden colour when cooked and a particularly sweet flavour when sautéed.
Eye irritation can be avoided by cutting onions under running water or submerged in a basin of water. Leaving the root end intact also reduces irritation as the onion base has a higher concentration of sulphur compounds than the rest of the bulb. Refrigerating the onions before use reduces the enzyme reaction rate and using a fan can blow the gas away from the eyes. The more often one chops onions, the less one experiences eye irritation."
Taken from wikipedia's page at: http://en.wikipedia.org/wiki/O...