Are onions and garlic related?

In this article, we will answer the question “are onions and garlic related”? and discuss answers to other related questions like where do onion and garlic come from and can you substitute garlic for onion. 

Are onions and garlic related? 

Yes, garlic and onions are related. Both onion and garlic belong to the genus Allium. Genus Allium is a subtype of the family Amaryllidaceae, and it is quite extensive.

Chives, shallots, and leeks are the other members of the Allium genus. If you’re wondering about spring onions, they’re just very young,  onions that have just sprouted.

Can you eat one if you’re allergic to the other?

Although onion and garlic share the same genus they do not belong to the same species. If you have an onion allergy it does not mean you have a garlic allergy too, unless your doctor specifies this. Let’s clear this together. 

The onion belongs to the species Allium cepa under the genus Allium. Meanwhile, the garlic belongs to the species Allium sativum under the genus Allium. This means that there is a certain difference between the two plants, and both plants do not have the same allergic reaction.  

But it is best for you that you should avoid both of them if you know you are allergic. Just to be on the safe side. However, you should ask your doctor to perform a detailed test, to see whether you are allergic to all plants in the Allium genus, or just a specific species within that genus.

We recommend this mostly because no one can avoid everything from genus  Allium, otherwise, your life would be very difficult. It is present in everything and in every culture so avoiding it is not easy at all.

Where do onions and garlic come from?

Both onions and garlic belong to the same genus, so we should first take a look at where the Allium first came to be. It is a very common plant genus and can be found across all continents, within the entire Northern Hemisphere.

In Asia. Most of the species of the genus Allium have been discovered here. If you look at the history, you came to know that China used onions back in 5000 BC. There are other, more recent recordings from ancient Persia and India.

Garlic grows predominantly in Central Asia and northern Iran, since then it has become as common as onions. China is still the biggest onion and garlic producer. 

Can you substitute garlic for an onion?

Even though both go so well together and belong to the same genus, they both provide different flavours. So should you substitute them or not?

The answer is you can substitute them if you have nothing else to help you, but you will not get the desired results. You see, onions and garlic do not cook the same and have a different level of pungency.

A chopped and fried onion will lend its flavour to an entire pot of stew but garlic can not even after being simmered for 3 hours.  You need a whole lot of cloves, about as much as you would use onions.

Garlic has a sharp pungent smell as opposed to the onion that has mostly a sulfur, mellow smell. Both have a different flavour.  

Other FAQs about Onions which you may be interested in.

Can you eat an onion after it’s been cut?

Are onions a fruit or vegetable?

Can we fry garlic and onions at the same time? 

The answer is no. You cannot fry garlic and onions at the same time. When you cook something that requires both onions and garlic, do your best to fry them separately. Because if you chop onions and garlic and throw them in the hot oil at the same time, the garlic will burn by the time the onions start to soften.

Why? Because onions have higher water content as compared to garlic and also have thicker cell walls. Onions take more time for frying so that the cell walls soften and the water can be released. Garlic burns much more quickly.

This all means that when you’re cooking with both, first wait for the onions to be completely done. This can take up to 10 minutes, depending on what you’re cooking. Then, at the end add the chopped or crushed garlic. Only let it fry for about 30 seconds until it gets nice and fragrant.

When you are cooking you should notice when the garlic smell is starting to fade and turn into a burnt smell. Stop before that point. Then proceed with cooking as usual.

Are garlic and onion safe to eat? 

Generally, garlic is safe to eat, but some mild side effects have been reported. According to Oregon State University, the most commonly reported side effects of eating garlic and taking garlic supplements are bad breath and body odour. Some people also have gastrointestinal issues such as constipation, nausea, flatulence, diarrhoea and vomiting.

Eating garlic in certain forms might also interact with some medications. Ingesting garlic may interact with nonsteroidal anti-inflammatory drugs, blood-thinning medications, medications for HIV and AIDS, birth control pills and a few others. Speak to your doctor before taking garlic supplements or increasing how much of it you eat to be safe.

When you eat onions, their tear-jerking smell might be your biggest risk. No significant side effects to eating them have been reported, according to the Food Science and Nutrition umbrella review. We hope you enjoy adding these two delicious vegetables to your diet; they can be a benefit to your health.


In this article, we answered the question “are onions and garlic related”? and discussed answers to other related questions like where do onion and garlic come from and can you substitute garlic for onion. 


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.