Do onions become poisonous after being cut

In this brief guide, we will address the query, “do onions become poisonous after being cut?” We will also discuss what is the origin of this myth and what makes onions smelly.

Do onions become poisonous after being cut?

No, onions do not become poisonous after being cut. However, it is easier for bacteria to grow on cut onions, and then it is dangerous to eat them as they can cause foodborne illness.

This myth has been spread because it was affirmed that bacteria will grow at a rapid rate, causing rapid spoilage. But this can not be true, the juices produced by onions are charged with antimicrobial compounds which makes this theory not accurate.

The idea of poisonous cut onions first originated in 2008, but as time and research have demonstrated, it is just not possible. So, do not worry about consuming chopped onions, if you guarantee proper storage, you can eat them without any problem even after 7 days!

Are onions prone to be infected by microbes?

No! Onions are well-known for their antimicrobial activity, which is another reason to discard the myth of poisonous onions. The reason why this occurs is that onions, and garlic, are rich in organosulfur compounds, also responsible for the strong smell of these species.

Organosulfur compounds have been demonstrated to exhibit diverse health benefits, such as

  • Anticarcinogenic properties. It has been found that several organosulfur compounds can reduce the rate of tumors.
  • Rich in antioxidants. It is recommended to consume these ingredients to prevent the effects of aging.
  • Anti-inflammatory properties. It has been found that these compounds can reduce the risk of inflammation as they can inhibit the production of compounds responsible for inflammatory response.
  • Antibacterial properties. These compounds have been also proven to reduce the bacterial growth in onion, garlic, and other species with organosulfur compounds.

If you want to learn more about the effect that organosulfur compounds bring on your health, you can click here.

Why do onions cause tears?

Not everything is perfect when talking about the organosulfur compounds contained in onions. We all are familiar with the uncomfy sensation that cutting onions provokes, your eyes can not stop crying when exposed to the strong odor!

 But let’s explain it with a little more science, when you cut onions all the organosulfur compounds will be liberated into the environment, so they can easily reach your eyes. When exposed to these compounds, your lachrymator substances will be affected.

What organosulfur compounds cause to your eyes is that they alter the amino acids the lachrymatory agents, this will cause irritation, and the eyes will tear to remove the form of acid that has formed. 

Luckily for us, there are alternatives to prevent this weird sensation, you can click here to read more about it.

Can you store cut onions?

Although in 2008 it was published that cut onions can be poisonous to human health, later findings have demonstrated that this claim is not scientifically approved. Something you need to keep in mind is that, after cutting an onion, it MUST be stored at cold temperatures

You can freeze or refrigerate chopped or diced onions, depending on how long you want to keep them. Cut onions are no longer protected by all the layers of whole onions, so their shelf life reduces to 7 to 10 days.

To guarantee that shelf life, it is important to place the cut onions in sealed containers, like freezer bags. Do not leave them uncovered in the fridge! All of the other items will catch the characteristic onion smell, and it will not be pleasing!

How long do cut onions last?

Whole onions exhibit a large life, compared to other fresh ingredients as they can last for up to 1 to 3 months. 

The key to a large shelf life is keeping proper storage. If you have chopped or sliced onions, their shelf life will be reduced to only 7 to 10 days. 

How can you tell when cut onions have gone bad?

Even though the estimated shelf life has not ended, you need to check daily for any spoilage signs because consuming spoiled food will cause severe symptoms, you can read more about this subject here

Make sure you check for any of these signs

  • Changes in their appearance.
  • Mold growth.
  • Off smell.

You will easily notice when onions are no longer safe for your consumption, do not consume spoiled food!

Can you eat cut onions that have gone bad?

No, eating any kind of food that has gone bad can lead to severe symptoms that can even put your life at risk. Consuming spoiled food will expose you to several harmful compounds produced by microorganisms.

Do not take it easy and be very strict when checking for any sign of spoilage in your food.

Other FAQs about Onions  that you may be interested in.

What do onions do for you?

Can you bake a blooming onion

Can dogs eat small amounts of onion?


In this brief guide, we have addressed the query, “do onions become poisonous after being cut?” We have also discussed other queries related to the subject at hand. 

Hope you found this blog useful. If you have any questions, please let us know.


Hi, I am Charlotte, I love cooking and in my previous life, I was a chef. I bring some of my experience to the recipes on this hub and answer your food questions.