| MadSci Network: General Biology |
My original guess as to why onoins make you cry was that they contain capsaicin the molecule that makes red peppers hot, and the active ingredient in mace and tear gas.. However, courtesy of the Walla Walla Sweet Onion page, it seems that the sulfur content of the onion is to blame. 'Sulfer' is a fairly generic term, and I haven't been able to find out what sulfur-containing compound is the culprit. Most proteins in your body contain sulfer. Many type of sugars produced in plants and animals are 'sulfated.' Certainly sulfuric acid is a noxious irritant to the eye, but I have found no evidence that onions produce it. Sweet onions such as the Walla Walla and the Vidalia sweet onion boast decresed sulfer levels and thus no tears.
As to chopping off the roots, I have heard the same suggestion and tried it. To my sensitive eyes it seems to make little difference. I can suggest soaking your pungent onion in cold water for 10-15 minutes before making a close approach.
-Nick