1 Pain that does not diminish with rest, and pain that may be worse at night than during the day. 2  Back pain along with constitutional symptoms, such as loss of appetite, unplanned weight loss, nausea, vomiting, or fever, chills or shakes.
Unstable chemicals. Onions produce the chemical irritant known as syn-propanethial-S-oxide. It stimulates the eyes' lachrymal glands so they release tears. Scientists used to blame the enzyme allinase for the instability of substances in a cut onion.
How to Chop and Slice Onions. Rinse the onion thoroughly under cool tap water. On a cutting surface, use a chef's knife to slice off the stem and root ends. Remove the papery outer skins and cut the onion in half from the top end to the root end.