why do apple make you cry

The Deep Dive

When you cut an onion, you rupture its cells and release enzymes called alliinases. These enzymes convert amino acid sulfoxides into volatile sulfur compounds, most notably syn-propanethial-S-oxide. This gas floats upward and dissolves into the thin layer of moisture on your eye surface, forming a small amount of sulfuric acid. Your corneal nerves detect this irritation instantly and signal the lacrimal glands to flush the eye with tears as a protective reflex. Apples belong to an entirely different botanical family and contain no significant concentrations of sulfur-based amino acids or the enzymes needed to produce lachrymatory compounds. Their chemistry revolves around sugars like fructose, organic acids like malic acid, and aromatic esters that give them their characteristic flavor and fragrance. Some people report mild eye stinging when exposed to extremely tart or acidic apple varieties, but this is a rare sensitivity to volatile organic acids, not the potent chemical warfare that onions wage. The confusion likely persists because apples and onions are both common kitchen staples sliced and diced regularly, and cultural references sometimes blur the line between them.

Why It Matters

Understanding the actual chemistry behind tear-inducing foods helps cooks choose smarter preparation methods. Knowing that onions are the real culprit, people can chill onions before cutting, use sharp knives to minimize cell damage, or cut near ventilation. This knowledge also highlights how plant biochemistry evolved as defense mechanisms against herbivores, and how humans have learned to work around these defenses to enjoy nutritious foods without unnecessary discomfort.

Common Misconceptions

The most widespread misconception is that all pungent or sharp-tasting fruits and vegetables make you cry. In reality, only a narrow group of Allium-family plants, including onions, garlic, and leeks, produce the specific lachrymatory sulfur compounds responsible. Another myth is that crying while cutting onions is an allergic reaction. It is not an allergy at all; it is a direct chemical irritation that affects virtually everyone equally, regardless of allergy status.

Fun Facts

• Chewing gum while cutting onions can significantly reduce tears because it encourages mouth breathing, drawing the irritating gas away from your eyes.
• New Zealand scientists developed a genetically modified onion called the Sunion that produces far fewer sulfur compounds, making it virtually tear-free when sliced.