Are Onions the Root Cause of Your Migraines or Bellyaches?

Humans are partial to the flavors of onions and garlic. These aromatic vegetables, as well as their relatives in the allium family – such as spring onions, leeks, and chives – show up in nearly all cuisines in the world. Either fresh, cooked, or in the form of onion and garlic powder, these veggies have completely taken over our food and our tastebuds.

And for the many people who are sensitive to allium vegetables, this poses a serious issue. Not only is it difficult to find foods in supermarkets and restaurants that contain no onions or garlic, but because these vegetables are everywhere, catching an allium intolerance can also feel like an uphill battle.

If you’ve ever had unexplained stomach issues, hives, or headaches that come seemingly out of nowhere, we highly recommend that you read this article carefully. These are all common symptoms of allium sensitivity, which is not the same as an allergy.

Allium intolerance - what is it?

Allium Sensitivity red onion on a plate

Food intolerance makes it difficult for a person to digest certain foods. It may also lead to unpleasant symptoms – both digestive and not. Lactose and gluten intolerances are both great examples of food intolerances.

The same is true for intolerance to alliums. It happens when a person consumes foods that contain onions, garlic, chives, and other vegetables from the allium family. The severity of the intolerance varies from person to person. Symptoms may appear almost immediately or show up to 2-3 hours after ingesting the food. The individual may start experiencing a range of unpleasant symptoms, such as:

  • Digestive issues - nausea, stomach pain, vomiting, bloating, flatulence, and diarrhea.
  • Migraines - dizziness, lightheadedness, and headaches 
  • Hives or an itchy rash on the body
  • Swollen lips, tongue, throat, or face
  • Nasal congestion
  • Trouble breathing
  • Very rarely, anaphylaxis.
Allium Sensitivity chopping vegetables
Although it’s difficult to estimate how many people have allium intolerance since most are likely to be unaware of the condition, health experts consider it to be rather common.

Alliums and irritable bowel syndrome (IBS)

Apart from cases of food intolerance, alliums often trigger digestive symptoms in patients with IBS. That’s because onions and garlic contain a type of FODMAP called fructan. This carbohydrate is one of the most common causes of bloating or diarrhea among IBS patients. Fructan draws water into the intestine, which leads to diarrhea, gas, and bloating. Just how common is this? A study from 2018 stated that 60% of their participants experienced IBS symptoms after eating onions.

Allium Sensitivity woman with an upset stomach

Meanwhile, the American College of Gastroenterology reports that 10-15% of the world population suffers from IBS. So, even if we assume that not all IBS sufferers are sensitive to alliums, we’re still left with hundreds of millions of people who cannot tolerate onions and garlic.

Read more about IBS here: IBS vs. IBD - How Are They Similar and Different?

Allium allergies

True allium allergies are much rarer than intolerances and IBS, but they do occur. Researchers estimate that around 1% of the world's population has a genuine onion and garlic allergy. As awareness of the condition is rising, so is the number of cases of food allergies and intolerances to alliums.
Allium Sensitivity brown onion

So how are true allergies different from the other conditions we listed? To be brief, allergies are a rapid immune response to a harmless ingredient – in this case, onions and garlic. People with severe onion allergies don’t even have to eat the alliums to get an immune reaction; for some, it’s enough to touch a knife used to chop onions or be in the same room as someone crushing garlic. Moreover, many allium allergy sufferers are also sensitive to flowers related to onions, such as tulips, irises, and lilies. 

Unlike food intolerances, allium allergies appear in a matter of minutes. They are also more likely to be lethal. That’s because the entire body reacts to the trigger, including vital organs like the lungs, kidneys, and the cardiovascular system.

How to detect an onion sensitivity

In the case of allium intolerances or digestive reactions, symptoms can be subtle and difficult to spot. For instance, someone with an onion intolerance may be fine eating cooked onions but not raw ones. Another individual may tolerate a small portion of onions, but experience symptoms as soon as they eat more.
Allium Sensitivity doc

Usually, doctors recommend an elimination diet to test whether or not your body is sensitive to a specific food. However, onions, leeks, and garlic often hide in unexpected foods – such as condiments, flavored snacks, and sauces. It’s not uncommon for onion or garlic powder to be omitted from the ingredient list or the restaurant menu. So is there a way to figure out whether or not you have an allium sensitivity?

A doctor can guide you through the process. The diagnosis may involve blood work and allergy testing. And while you wait for your appointment, we recommend that you keep a food diary where you write down your daily menu and how it makes you feel. A diary will help you narrow down the list of food suspects that trigger your symptoms.

Tips for replacing onions and garlic

Allium Sensitivity red onions

Those with allium intolerance or IBS may find it most beneficial to avoid the food trigger altogether. However, this may prove challenging, especially when you eat food you haven’t cooked yourself. You can talk to the server or chef while eating out and ask for food without the culprits.

Home-cooked meals are much easier to manage. Here are a few practical tips:

1. Garlic or onion powder can often be replaced with other spices like ginger, cumin, lemon juice, coriander, or horseradish.
2. If you’re preparing a dish that uses sauteed garlic or onions, you can play around with caramelized bell peppers, miso, soy sauce, or celery.
3. In soups, a similar savory taste can be achieved with fish sauce, soy sauce, miso, or celeriac.

References: Healthline, Huffpost, Medical News Today

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