HealthDay operates under the strictest editorial standards. Our syndicated news content is completely independent of any financial interests, is based solely on industry-respected sources and the latest scientific research, and is carefully fact-checked by a team of industry experts to ensure accuracy.
- All articles are edited and checked for factual accuracy by our Editorial Team prior to being published.
- Unless otherwise noted, all articles focusing on new research are based on studies published in peer-reviewed journals or issued from independent and respected medical associations, academic groups and governmental organizations.
- Each article includes a link or reference to the original source.
- Any known potential conflicts of interest associated with a study or source are made clear to the reader.
Please see our Editorial and Fact-Checking Policy for more detail.Editorial and Fact-Checking Policy
HealthDay Editorial Commitment
HeathDay is committed to maintaining the highest possible levels of impartial editorial standards in the content that we present on our website. All of our articles are chosen independent of any financial interests. Editors and writers make all efforts to clarify any financial ties behind the studies on which we report.
WEDNESDAY, July 5, 2017 (HealthDay News) -- Ever wonder why your eyes fill with tears when you chop an onion?
One eye doctor pinpoints the culprit.
Onions use sulfur in the soil to create amino acid sulfoxides, which are sulfur compounds that readily turn into a gas. When an onion is cut open, it releases the sulfoxides and enzymes, which react and create a gas called syn-propanethial-S-oxide.
Because onions grow underground, this gas helps deter critters that want to feed on them.
But the gas is also what causes your eyes to water when chopping onions, said Dr. Robert Rosa Jr., an ophthalmologist at the Texas A&M College of Medicine.
"It really is a complicated chemical process that creates the gas," said Rosa. "They all act as precursors that create the lachrymatory processor -- or what makes you tear up."
White, yellow and red onions all have higher concentrations of the onion enzyme necessary to create this gas, while sweet onions, green onions and scallions have lower concentrations. Also, some people are more sensitive to this gas than others, he said.
"Your eyes have a set of nerves that detect anything that's potentially harmful to your eyes. Your eyes react to the gas that is formed, and your eyes try to flush it out with tears," Rosa explained in a school news release.
However, onions pose no serious threat to your visual health.
"Chopping onions can cause some burning and irritation and tears. Other than that, it's pretty safe on your eyes. It's a temporary sensation with no known long-term effects, nor will it worsen any other conditions, like pink eye," Rosa said.
Goggles can prevent the gas from reaching your eyes while cutting onions, but they aren't really necessary, he added.
"Some people may cut the onions in a bowl of water," Rosa said. "I'd personally recommend using eye drops, like comfort drops, to help lubricate or rinse the eyes and dilute the gas exposure to the eyes."
The U.S. National Library of Medicine has more on various vision problems.
This story may be outdated. We suggest some alternatives.
The content contained in this article is over two years old. As such our recommendation is that you reference the articles below for the latest updates on this topic. This article has been left on our site as a matter of historic record. Please contact us at firstname.lastname@example.org with any questions.
Updated on May 29, 2022