Saturday, November 15, 2008

Why Do Onions Make Us Cry?

Shanna from Altoona, PA, was helping her big sister prepare dinner one night, and she noticed that her eyes became really irritated when her big sister cut up an onion. She wrote in asking: why do onions make us cry? We will explore the answer to that question but we will also explore some methods that might minimize the eye irritation. Many people enjoy the taste of onions in their meals. In fact, the average American eats about 20 pounds of onions each year. Onions are healthy components of the human diet because they contain vitamins B and C, protein, calcium, and iron. They also contain quercetin (pronounced KWAIR-SUH-TEN), which is an antioxidant that works to neutralize harmful substances in our bodies that cause tissue damage and aging. In addition to being full of nutrients, onions are low in fat and sodium. However, if you have ever cut into an onion, it is likely that your eyes filled with tears because they became irritated just like Shanna described. But why does this happen? How can we enjoy the taste and benefits of onions without the tears? When you cut into an onion, an enzyme (a biomolecule that speeds up chemical reactions) is released into the air from the ruptured onion cells. This enzyme converts some of the proteins from the onion into sulfenic acids that then become a gas. These can then come in contact with your eyes. These acids contain sulfur compounds that are common eye irritants. The gas reaches your eyes and reacts with the water that keeps them moist. The eyes become irritated, and your brain reacts by telling your tear ducts to produce more water that helps keep the eyes protected. You may want to rub your eyes to help soothe the irritation, but this will only make the irritation worse since your hands may have onion juices all over them. Some people wear goggles to minimize any irritation produced when cutting onions, but some also try the different methods discussed in the Little Lion Experiment. Give each method a try to figure out which one works best for you so you can enjoy onions without any eye irritation!

Little Lion Experiment:

How can we enjoy the benefits and the great taste of onions without the tears? For this experiment, you will explore some methods that are thought to reduce the unpleasant eye irritation that occurs when cutting into an onion. You will need an adult present to help you with this, especially when cutting the onion. It is preferable to try these methods over 5 different days, but you can try each of these home remedies during the same time. Throughout each of these methods, keep track of whether your eyes were irritated when the onion was cut and try to determine which method works best for you.

Items Needed

  • 5 small onions with the outer layers peeled away
  • 1 lemon slice
  • Slice of bread
  • Sugar
  • Bowl of water
  • Access to a refrigerator
  • Knife


  1. Method 1: Put one onion into the refrigerator. After 30 minutes, take it out and cut the onion.
  2. Method 2: Put one onion into a bowl of water so that it is covered in water. Cut the onion while it is submerged in the water.
  3. Method 3: Put a lemon slice in your mouth. Then cut the onion (keeping your mouth open)
  4. Method 4: Put a bread slice in your mouth. Then cut the onion (keeping your mouth open).
  5. Method 5: Put some sugar in your mouth. Then cut the onion (keeping your mouth open with the sugar on your tongue)


Did any of these methods work to keep your eyes from being irritated? If so, which ones worked the best? Having the onion chilling in the refrigerator before cutting it, like in Method 1, is supposed to slow the release of the irritating gases. Keeping the onion under water while cutting it, like in Method 2, is supposed to keep the gases from even reaching your eyes. Keeping the sugar, bread, or lemon slice in your mouth while cutting the onion, like in Methods 3-5, is supposed to keep the gases from ever reaching your eyes since the food will absorb the gases. Try to remember these different methods each time you help out with the cooking at home. And remember to wash your hands after handling an onion since they will be coated in the onion's eye irritating compounds.