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.
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.
When an onion is sliced and the cell walls are broken, enzymes called alliinases begin a complex chemical reaction that results in the release of volatile gas known as the onion lachrymatory factor. This gets released into the air and eventually enters your eyes if you're hovering over the onion.