I wear contact lenses and also own a spare pair of glasses, so I decided to put this question to the test.Д«efore starting my experiment, I asked Dr. Some contact lens wearers swear their lenses provide a shield against eye-irritating onion fumes. Are people who wear contacts more (or less) affected? вЂњThat may give you a little bit of relief,вЂќ he says. Finally, put a few drops of preservative-free artificial tears in your eyes. DonвЂ™t use tissues, which may contain lotion and shed lint that can make the problem worse. If you cut an onion and start to cry, wash your hands thoroughly and blot your eyes with a clean paper towel, Dr. Reflexive tears вЂ“ These tears irrigate the eyes and flush away irritants.ДЄ healthy tear film - plenty of basal tears - helps prevent your eyes from becoming irritated in the first place, while reflexive tears help to wash away irritants and protect the eyes, Dr. Darryl Glover, an optometrist, author and speaker.Д«asal tears вЂ“ These tears lubricate the eyes and keep them healthy. Tears help to lubricate your eyes and protect them from dust and other irritants, says Dr. вЂњBut it packs a surprising punch for its size.вЂќ How do tears protect your eyes from irritants? вЂњItвЂ™s a very small molecule,вЂќ Block says of the noxious syn-propanethial-S-oxide. The tear glands ( lacrimal glands) in the eyes then make tears to wash away the irritant. The gas triggers pain receptors in the eyes and nose designed to protect you from chemicals, smoke and other dangers. The precursor and enzyme mix, creating an unstable chemical irritant.ДЄt room temperature, this irritant quickly becomes a gas that spreads through the air. The onion contains both the chemical precursor to the gas and an activating enzyme that floats in onion cells in little walled-off areas (vacuoles).ДЄn onion gets sliced, diced or bitten into. This creates syn-propanethial-S-oxide, a volatile gas that makes your eyes burn and fill with tears. Onions make your eyes burn for the same reason they make you cry: thanks to the combination of that chemical compound and the enzyme that synthesize when an onion is cut.

вЂњThis is a way for the onion to defend itself against predators,вЂќ he says. This helps keep the bulb from getting eaten by animals as it grows in the ground, says Eric Block, a distinguished professor emeritus at the University at Albany, food chemistry expert and author of Garlic and Other Alliums: The Lore and the Science. Onions contain a chemical compound and an enzyme that mix to release an irritating gas when the onion is cut. You grab an onion, slice in and, within seconds, your eyes begin to burn and tears spill down your cheeks. YouвЂ™re in the kitchen making gazpacho, whipping up some French onion soup or prepping a smorgasbord of burger toppings.

Syn propanethial s oxide