Why Onions Make Us Cry and Proven Ways to Stop the Tears

This post contains links to products hand-picked by us. When you click the link and make a purchase, we may earn a small commission with no additional cost to you.

Onions are a staple ingredient in numerous culinary dishes across the globe, loved for their flavor and versatility. However, cutting an onion often leads to a teary experience for many individuals. This phenomenon has intrigued scientists for decades, prompting extensive research into the root causes and potential remedies. In this article, we will explore the science behind why onions make us cry and present proven strategies to stop the tears.

Understanding the Culprit: Syn-Propanethial-S-Oxide (Propanethial S-oxide)

The primary cause of eye irritation while cutting an onion is a volatile sulfur compound called Syn-Propanethial-S-Oxide (propanethial S-oxide). This compound is released when an onion is cut and reaches our eyes through a gaseous state. When it comes into contact with the moist surface of our eyes, it forms sulfuric acid, causing a stinging sensation and prompting tear production as a protective mechanism.

Factors Affecting Tear Production

Though it seems like everyone experiences onion-induced tears, the degree of tear production can vary among individuals. Several factors contribute to this variation, including:

  • Onion Variety
    Different onion varieties contain varying levels of enzymes and amino acids, resulting in diverse tear-inducing potentials. For instance, yellow onions are notorious for their tear-inducing properties, while sweet onions generally cause fewer tears.

  • Age and Freshness
    Onions that are older or have been stored for a longer duration tend to release more enzymes when cut, increasing tear production. Fresher onions, on the other hand, have lower enzyme levels and may cause fewer tears.

  • Personal Sensitivity
    Individuals differ in their sensitivity to the propanethial S-oxide gas. Some people may produce more tears due to heightened susceptibility, while others may experience minimal tearing.

Proven Strategies to Reduce Tear Production

While the propanethial S-oxide gas release during onion cutting is inevitable, several proven strategies can help minimize tear production:

1. Use a sharp knife

The way an onion is cut can affect tear production. Chopping onions with a dull knife or crushing them can cause more cell damage, leading to increased enzyme release and subsequent tear production. Utilizing sharp knives and employing proper techniques can minimize the damage and reduce tearing.

Our Pick!
Easily restore and maintain a sharp edge with this 3-stage knife sharpener, ensuring precise cuts that reduce cell damage when chopping onions. Combined with the cut-resistant glove, you can confidently handle knives, minimizing tears and maximizing efficiency in the kitchen.

2. Wear Eye Protection

Using protective eyewear, such as goggles or safety glasses, can create a barrier between your eyes and the propanethial S-oxide gas. This physical barrier prevents or reduces contact, subsequently limiting tear production.

Our Pick!
Safely prepare your favorite dishes without shedding tears. These fog-free lenses provide a protective barrier for your eyes, keeping tears at bay while chopping onions. Enjoy tear-free cooking experiences every time.

3. Use Onion Chopper

Onion choppers typically employ sharp blades and a container to efficiently chop onions while containing the volatile chemicals that cause eye irritation. By swiftly and precisely cutting onions, onion choppers minimize the damage to onion cells, reducing the release of enzymes that produce irritating compounds

Our Pick!
Efficiently chop onions without the eye irritation with this handy kitchen tool. Its sharp blades and integrated container ensure precise and swift cutting while containing the volatile chemicals that cause eye irritation. Get perfect results every time while reducing the release of irritating compounds.

4. Cut Near a Ventilation Source

Positioning yourself and the cutting board near a steady airflow, such as a fan or an open window, helps disperse the propanethial S-oxide gas rapidly. This reduces the accumulation of the gas near your eyes, diminishing tear production.

Our Pick!
Stay focused and tear-free while chopping onions with this versatile clip-on fan. The powerful airflow will rapidly disperse the tear-inducing gas, allowing you to breeze through your culinary tasks with ease.

5. Chill the Onion

By placing the onion in a refrigerator or freezer for 10-15 minutes before cutting, the enzymatic reaction slows down. As a result, lesser propanethial S-oxide gas is released, decreasing tear-inducing fumes when you start cutting.

6. Use Water

Water can help minimize the impact of the propanethial S-oxide gas. Wetting the cutting board and the knife before slicing the onion can assist in trapping the gas and preventing it from reaching your eyes as quickly.


Cutting onions without shedding a tear has long been a challenge for home cooks and professional chefs alike. However, understanding the science behind onion-induced tears and employing proven strategies can significantly reduce tear production. Whether it’s chilling the onion, cutting underwater, or wearing eye protection, incorporating these methods into your culinary routine can help ensure tear-free onion preparation and enhance your overall cooking experience. So go ahead, embrace the science, and let your tearless onion cutting journey begin!