The onion is one of the most widely used ingredients in cooking. It adds sweetness, character, and an essential aromatic base to many recipes. However, one question keeps coming up: how to cut an onion without crying? The good news is that there are simple and effective solutions. By understanding why onions cause tears and adopting the right techniques, you will significantly reduce this discomfort while gaining precision. Difficulty Time Skill Key Tool ★☆☆☆☆ Easy 5 min Basic cutting Chef's knife 🧪 Why do onions make you cry? When you cut an onion, its cells break and release sulfur compounds. An enzyme present in the vegetable transforms these compounds into a volatile gas. Upon contact with the eyes, this gas reacts with the tear film to form a small amount of irritating acid. The eyes then produce tears to flush out this substance. The key principle: the less you crush the onion's cells, the less of this gas is produced. That is why a perfectly sharp knife is the number one solution. 🔪 Recommended equipment Perfectly sharp chef's knife — the most important tool Stable cutting board — with a damp cloth underneath to keep it from sliding Paring knife for finishing touches Mixing bowl to collect the pieces 👨🍳 CuisinerTelUnChef Tip A sharp chef's knife is safer and more precise than a dull one. It slices through the cells cleanly instead of crushing them, which significantly reduces the release of irritating gas. This is the most important tip in this guide. Always place your cutting board on a damp cloth to keep it from sliding. 👨🍳 The Chef's Method — Step-by-step Step 1 — Choose a sharp knife A well-honed blade cuts cells cleanly. A dull knife crushes the onion and releases more irritating gas. This is the most important tip. Step 2 — Chill the onion Place the onion in the refrigerator for 20 to 30 minutes before cutting. The cold slows down the release of volatile compounds. Avoid freezing it, however, as its texture would be altered. Step 3 — Keep the root end intact Cut only the top end. Leave the base (the root end) in place until the end of the cutting process. It holds the layers together and limits the dispersion of irritating compounds. Step 4 — Make the cuts Peel the onion and cut it in half lengthwise Place one half flat on the cutting board Make several horizontal incisions without cutting through the root end Then make vertical incisions in a fan shape Finish with perpendicular cuts to obtain an even mince 👨🍳 CuisinerTelUnChef Tip Use a rocking motion with your chef's knife: the tip remains on the board while the blade rocks up and down. This fluid, controlled movement is the foundation of all professional cutting techniques. The more you practice, the faster and more precise you will become. Check out our guide to vegetable cutting techniques to master all the cuts. Step 5 — Work quickly Fluid cutting reduces exposure time to the gas. Prepare all your equipment before you start and work in a well-ventilated space. 💡 Tips that actually work Ventilate the workspace — a small fan or range hood quickly whisks away the irritating gas Chill the onion — 20-30 minutes in the refrigerator before cutting Sharp knife — the number one solution, always Lightly moisten the board — can trap some of the volatile compounds Wear protective goggles — not very stylish, but very effective for large quantities Cut near an open window — moving air disperses the gases ❌ Myths to forget ❌ Holding a spoon in your mouth — no scientific evidence. ❌ Breathing only through your mouth — very limited effect. ❌ Chewing bread — a popular trick with no proven efficacy. The best solutions remain: sharp knife + chilled onion + good ventilation. 🔪 Different ways to cut an onion Slicing Thin strips for stir-fries, quiches, sauces, and onion soup. The most common cut. Brunoise Small, uniform dice (2-3 mm) for vinaigrettes, stuffings, and garnishes. A basic technique of French cuisine. See our cutting techniques guide. Rings Perfect for burgers, grilled dishes, and salads. Use a mandoline for perfectly uniform rings. Quarters Ideal for stews, oven-roasted dishes, and batch cooking. Julienne Long, thin strips for Asian salads and refined garnishes. 👨🍳 CuisinerTelUnChef Tip For perfectly uniform rings, use a mandoline set to the desired thickness. Be careful to always use the finger guard! For brunoise, the precision of your horizontal and vertical incisions is key — check out our cutting techniques guide. ❌ Mistakes to avoid ❌ Dull knife — crushes cells and releases more irritating gas. ❌ Cutting too slowly — prolongs gas exposure. ❌ Removing the root end too early — the onion falls apart and cutting becomes imprecise. ❌ Working without ventilation — gas accumulates in the room. ❌ Unstable board — risk of sliding and injury. ❌ Uneven incisions — causes uneven cooking of the pieces. 🌡️ Storing onions Whole onions — cool, dry place away from light (several weeks) Peeled onions — refrigerator in an airtight container (3-4 days) Sliced onions — refrigerator (2-3 days) or freezer (3 months) Caramelized onions — refrigerator (5 days) or freezer (3 months) See our zero-waste guide to use all of your onions. 🥗 Nutritional values (per 100g of raw onion) Nutrient Amount Calories 40 kcal Protein 1.1 g Carbohydrates 9 g Fat 0.1 g Fiber 1.7 g Onions are rich in quercetin (an antioxidant), vitamin C, and prebiotics that are beneficial for gut health. ❓ Frequently asked questions Why do we cry when cutting an onion? Because the onion's cells release an irritating sulfur gas that reacts with the eye's tear film. The less you crush the cells, the less you cry. Is cold effective? Yes. An onion chilled for 20-30 minutes in the refrigerator releases the volatile compounds responsible for tears more slowly. Which knife should I use? A sharp chef's knife is ideal for achieving a clean cut without crushing the cells. Should I remove the root end at the beginning? No. Keep the root end until the end to hold the onion's layers together and limit gas dispersion. Do protective goggles work? Yes. By preventing gas from reaching the eyes, they are very effective, especially when preparing large quantities. How do I get a perfect brunoise? Check out our vegetable cutting techniques guide to master brunoise and all professional cuts. 🔗 Related guides and recipes 🔪 Vegetable Cutting Techniques — brunoise, julienne, chiffonade 🥦 Cooking Vegetables — how to cook onions 🌿 Herb and Spice Guide — aromatic pairings with onion ♻️ Zero-Waste Guide — use all your onions 🇫🇷 French Cuisine Guide — onions in classic dishes 🐟 Fish Guide — onion as an aromatic for fish 🛒 CuisinerTelUnChef tools to slice like a chef Our chef's knives — the number one solution to stop crying Our cutting boards — stable and secure surface Our mandolines — for perfectly uniform rings Our zesters — for finely grating aromatics as a finishing touch