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What Are the Symptoms of an Onion Allergy?

By Kathleen Howard
Updated Mar 03, 2024
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While onions are not one of the more common food allergens, it is possible for both children and adults to suffer from an onion allergy. Symptoms of an onion allergy include flu-like symptoms, rash and inflammation. Depending on the severity of the allergy, sufferers can also develop a serious condition known as anaphylaxis. Allergy symptoms might appear almost immediately or occur several hours after consumption. Onion allergies can develop during childhood or later in life and might be accompanied by an allergy to garlic, chives and other members of the Allium family.

Many people who suffer from these allergies experience flu-like symptoms shortly after consuming onions. These symptoms frequently include upset stomach, diarrhea and nausea. Individuals who do not suffer from diarrhea might instead become constipated and bloated. Many people also experience headaches, sinus pain and trouble sleeping. Symptoms range from mild to severe and can last for several hours after consumption.

An allergy to onions might also produce several common symptoms of allergies, including hives, itching and inflammation. The lips, throat and face might become swollen, red and tender to the touch. It is also common for the eyes to become watery and irritated.

While rare, an onion allergy might lead to a condition known as anaphylaxis in some sufferers. Anaphylaxis is a serious medical condition that can cause changes in heart rate, difficulty breathing and unconsciousness. A person suffering from this condition might suddenly become lightheaded, confused or very swollen. People who believe they might be suffering from anaphylaxis should seek immediate medical attention as this condition can be fatal.

The symptoms of an onion allergy can develop anywhere from minutes to hours after consuming onions. Depending on the severity of the allergy, some individuals will experience symptoms after just cooking with onions or eating onion-flavored foods. Others can consume cooked onions without incident, but develop symptoms after eating raw or undercooked onions. It is also important to remember that individuals who are allergic to one type of onion might be sensitive to several types of onions. People who have allergies might also be allergic to other members of the Allium family, including chives, garlic and scallions.

While some people might begin showing signs of an onion allergy during childhood, others do not develop this allergy until adulthood. It is possible to suddenly develop an allergy after consuming a certain food for years. Since this can make it difficult to pinpoint the allergen, sufferers might need to contact a physician or specialist experienced in diagnosing food allergies to help determine the cause of their symptoms.

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Discussion Comments
By anon994330 — On Feb 01, 2016

To Post #4: Your story is exactly mine. I actually paused thinking maybe I had written it. Mine also started almost 20 years ago with hives during pregnancy. Took Claritin after I delivered. I am allergic to mustard, tomatoes, garlic and raw onions cause extreme fatigue. Sometimes Chinese mustard will also cause fatigue but not as bad as onions. Red onions are possibly the worst, although I had yellow onions yesterday and was knocked out. I can't eat scallions without allergic issues either including upset stomach.

By anon991030 — On May 21, 2015

I puréed onions to put in ground turkey to add flavor. I know I can't eat uncooked onions. I get swelling behind my right eye, headache and nausea if I do. I thought cooking raw onion with the turkey burger would be OK. I think maybe whatever normally cooks off when cooking onions solo was trapped inside the turkey burger. I got so sick for about six hours. I can only eat raw Vidalia onions, none of the other ones. I'm not going to try this again.

By anon937016 — On Mar 03, 2014

I get extreme fatigue when I eat onions, most profoundly raw onions. I could easily sleep for several hours even in the middle of the day when I should not feel tired. Also, my eyelids feel very heavy with a slight burning sensation.

When I first developed an onion allergy almost 20 years ago during my first pregnancy, I saw pretty bad hives which I treated with Claritin. The hives have almost subsided, but now exhaustion has been the main thing I am dealing with for the last several years. I think it is time to give up onions entirely before it becomes worse.

By the way, I also developed reactions to tomatoes, garlic and mustard around the same time. Salsa and mustard still bring about hives more so than any other foods. If I drink something acidic along with any of these foods, especially onions, I often experience bloating and nausea.

By bear78 — On Jul 09, 2013

I'm allergic to raw onions. When I eat them, my bottom lip swells and the inside of my mouth itches. Thankfully, my throat has never swollen.

I don't react this way to cooked onions though, I don't know why. I think I'm allergic to the acid in raw onion juice which somehow becomes ineffective when it's cooked. I avoid raw onions completely.

By ZipLine — On Jul 09, 2013

@fify-- It's probably an allergy. Do you experience any other symptoms like bloating, nausea, diarrhea or fatigue along with the migraine?

Allergies come in different intensities. Not everyone has anaphlyaxis as an allergic reaction. People can have different symptoms, and can experience them in different ways.

One thing you can do is eliminate onion from your diet completely for several weeks and see if you experience migraines during this time. If not, have one meal with onion and see it brings on a migraine. If it does, you are allergic.

You can definitely get an allergy test as well but sometimes food allergy tests are not reliable. You may test negative but might still have a mild allergy to that food. So you have to listen to your body. Keeping a journal of symptoms is a good idea.

By fify — On Jul 08, 2013

I've noticed that whenever I eat a meal with onions, I develop a bad migraine afterward. I've experienced this several times now and I'm starting to think that it's not a coincidence. Could it be an allergy?

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