Onion allergy symptoms and how to tackle them

Onion allergy – what is it?

Onion allergy is a condition in which after consumption of onions the body starts reacting in an unwanted manner. Similar to all other allergies this allergy is also triggered when stimulant (onion) is consumed by allergic people. About 3% of the US population is allergic to onions. In most cases onion allergic people are also allergic to garlic. Studies have indicated that raw onions cause more allergy than cooked ones.

What happens when allergic people consume onion?

Onion contains many proteins. These proteins react with the IGE antibodies present in our body and trigger the mast cells. These mast cells are mainly present in the skin, pharynx and gut. Upon reaction with the proteins these mast cells release histamine which causes adverse reactions in the body. Therefore it can be concluded that the major cause of onion allergy is histamine.

Onion allergy symptoms

The symptoms of onion allergy are very much similar to other allergies. The symptoms may appear at different times after the consumption of onions. There is a huge gap in the timeframe and a person may experience the symptoms immediately after the consumption or within a span of two hours. Onion allergy symptoms are vomiting, nausea, diarrhea, redness or skin inflammation, sudden swelling, stomach cramps and eye irritation.

In many cases a person may not be allergic but is intolerant to onions. Such person may suffer from some small problems when onion or garlic is being cooked. These are problems like burping, burning sensations in mouth, blisters in mouth, gums or throat. These people have the difficulty in digesting onions. Therefore it is a necessity to identify whether the person is intolerant or allergic to onions. You can identify your intolerance by blood tests and allergy tests.


It has been rightly said that prevention is better than cure. Therefore the best treatment is to avoid the consumption of onions. An onion allergic person must be overcautious about what he eats because onion is an integral part of many recipes and sometimes though it is not used directly but its derivatives may be present. People with such allergy must go through the list of ingredients present on the packets of each processed food and also take special care when eating outside.

But if there is an accidental exposure to onions then antihistamine medication or injection of epinephrine is used. In the presence of skin reactions only ointments and corticosteroids is helpful.


Onion allergy may not be very common but for allergic people it is a very big problem. Allergic people may find it very difficult to control the consumption of onions. Though the US food and drug department has not recognized onion as a major allergen but to an onion allergic person it might turn out to be dangerous. Allergic people may develop the condition of ‘anaphylaxis’ which causes dizziness, faintness, difficulty in breathing, loss of conscience, hives, rapid heartbeats and swelling. People suffering from anaphylaxis need immediate medical attention such as a shot of epinephrine. Allergic people must abstain from onions. This is the most difficult part as almost all major food items are prepared using onions.

40 thoughts on “Onion allergy symptoms and how to tackle them”

  1. With a lifelong onion allergy, I’ve found one of the best helps is children’s Benadryl (diphenhydramine).
    If I discover onion ingredients after I’ve eaten something, drinking liquid Benadryl seems to work fastest to prevent stomach cramps and that lovely burning pain sensation that I’ve somehow poisoned myself.
    Dunno about trying it after having an otherwise lovely four-course meal with wine though!

    1. I newly discovered this onion problem and it is a BIG problem. I am going to try the children’s liquid Benadryl next time. I know exactly what you mean about the stomach cramps and the feeling that you’ve somehow poisoned yourself. The tiniest bit of onion will make me feel this way for 2 or 3 days! Thanks for the tip.

  2. Few people can relate to an extreme onion / garlic intolerance. For me it seemed to come on suddenly but I think perhaps garlic was the cause of IBS for years. Now within no time at all after a meal I can sense “I’ve been garlicked!” And it does feel like having been poisoned. I can then expect a 10-15 hour belly-aching session into the night. Lots of upper abdominal cramping and indigestion. For me this is paired with this sensation on my tongue or IN my tongue whee garlic or onion taste is just permeated throughout and no amount of brushing my tongue and mouthwash can remedy it. I’ve yet to hear anyone mention this tongue symptom that is so prominent for me.
    My remedies are; 4 ounces of Apple cider vinegar with a teaspoon of baking soda and gulp it down to aid in digestion but it’s not a tremendous help. I have hot water and or hot tea (peppermint, ginger, yogi stomach tea), I chew lots of peppermint gum and I take several digestive enzymes. All of this just to try and sleep through the night with the discomfort. And then the next day my stomach is off and my visits to the bathroom not so pleasant. ):

    1. Oh I hear ya on that!!!! That was me this weekend due to a potluck turkey dinner. By the time I had gone to bed I looked nine months pregnant. And the pain!!! T1’s help but I have had to take T3’s before. And nothing really helps until it goes through my system. :(

  3. Very helpful information. I have always disliked onions my who whole life and when I would taste them I would almost immediately vomit. I thought it was more of a mental reaction to them. A few months ago I forced myself to try something with cooked onions in it and even though I hated the taste I carried on. Within about an hour my stomach was feeling terrible so I took some pepto and went to bed. About two hours in I woke up drenched in sweat, hives all over my chest, swollen eyes and wasn’t able to get a full breath of air. I went to the local urgent care and was given a shot of Benadryl which helped quite a bit.

    Last night I was on a 2nd date and had a pizza and and within an hour my stomach started to turn. shortly after I started to develop the same symptoms as above. I went to the same urgent care again and was given a Benadryl shot again which helped. The Doctor recommended me to follow up with my doctor and suggested I start to keep an epi pen somewhere nearby for the future. I have noticed that my symptoms are stronger and faster with each time I am exposed. (I have no reaction to garlic either)

  4. I am 27 years old and never had an allergy reaction. Sometimes, the common sneeze, stuffy nose, or sinus pressure stuff. Three weeks ago i started breaking out into hives, having trouble breathing, and itching like crazy everywhere. The 1st time it happpend, i was going to be in a wedding in a couple of days so went to my work clinic to see what was going on. The next day it happened again and the breathing problems got a lot worse so i had to take a trip to the ER. I have had bad reactions a total of 6 times in 3 weeks!!!Finally I got an apt with the allergist. I went there for the skin test (poked 120 time) to find i am allergic to Onions and Garlic. I WAS NOT HAPPY!! Onions and Garlic are my life, it seems to be in everything. Now i am stuck panicking every time i take a bite of something wondering if i am going to break out into hives and stop breathing. I made my favorite Squash, Mushrooms, Bell Peppers, and Zucchini with just a dash of Season Salt and this caused me to wake up with hives all over my legs, chest, neck and face. I am in desire need of some pointers and list of foods WITHOUT ONION or Garlic. :(

    1. I also have a reaction to bell peppers. Not as strong as onion, but I will have stomach problems. I dont know if this will help, but maybe the season salt? I never put season mixes on my food.

    2. Sorry to hear about the recent discovery – it crucifies a good friend of mine. Being a bit of a foody I’ve taken the challenge to cook stuff that he misses eating (because if it didn’t have onion in before companies add it to recipes without mentioning it!) even something as simple as a decent gravy is hell for him to find. As stated, avoid ready-made spice mixes!!
      However, if there’s some that you really like take a look at the ingredients list; write down the spices and just omit the onion powder/concentrated onion that is almost guaranteed to be present – mix it up in bulk from dried spices and keep it in a cliplock box.
      My friends allergy is relatively servere – his whole jaw and his throat swell badly within minutes of minute consumption – he can’t inhale it either.
      Some things you may find you can get away with are Beef Oxo cubes, Bovril (beef drink) and Chicken Oxo (Don’t know if you’re UK/US based or a stranger to Oxo but they’re a well-known british brand of stock-cube). They claim onion powder on the ingredients list but it must be so minute that it doesn’t affect him. On a plus, he can eat garlic like its candy.
      I hope you have some luck finding the onion-free options. My friend has turned it into an advantage to find some truly great eating spots who give a toss what ingredients their customers can eat – do the same :)
      In onion based dishes I substitute onion for garlic, i.e. chicken/beef and onion gravy becomes caramalised garlic with meat flavour. I use approx 2-3 cloves of garlic per large onion depending on portion sizing of course.

  5. I am just wondering can an onion allergy be to just certian types of onion or is it that all of a sudden I have become allergic to them?

  6. I’m doing a project at college about the impacts of onions on health, I wondered if anyone had any information I could maybe include about this allergy, it sounds really horrible! :(

    1. Hi, in regards to your research, my family has 6 members who are all allergic to onions, some severly. Daughter has IBS and onions of any type make her deathly ill. All 3 of her children are allergic to onions. Recently another Grandson in the family has shown severe reaction to onions. Just doing some online research into this issue , trying to understand why the reactions to onions and ran across your info.

    1. I always get sinus headaches from both smelling onions and eating them. This is not surprising, however, because for those of us who are intolerant to onions we release histamines in response to exposure to them. Anti-histamines would be a logical remedy to our reaction. I not only suffer from sinus headaches from onions, but I have gas, bloating, nausea, diarrhea, and onion taste in my mouth that I can’t get rid of by brushing my teeth or using mouthwash. It’s impossible to slip onions past me because within just a few minutes I get the headache and the taste on my tongue followed by frequent trips to the bathroom that start before the meal is even finished.

      1. As a follow up to this, I found the following article helpful for more information. http://thatpaleoguy.com/2011/11/14/histamine-intolerance-update/ Quoted from the article: “Histamine is a chemical which occurs naturally in certain foods. This is also one of the chemicals that is released in the body as part of an allergic reaction, causing the typical ‘itching, sneezing, wheezing, swelling’ allergy symptoms. We all have an enzyme (Diamine oxidase [DAO]) which breaks down any histamine that we absorb from a histamine-containing food, so when we eat a food which contains histamine it does not affect us. However some people have a low level of this enzyme, and when they eat too many histamine-rich foods, they may suffer ‘allergy-like’ symptoms such as headaches, rashes, itching, diarrhoea and vomiting or abdominal pain. This is called histamine intolerance. Some studies have also suggested links between histamine intolerance and urticaria, asthma, eczema and anxiety and panic attacks.”

  7. I have reactions to older onions. I can’t drink alcohol and believe I have reactions to corn and wheat too. But older onions for some reason affect me similarly to alcohol. Immediate violent reaction.
    Thanks for this article!!

  8. I’ve had onion allergies for about 15 years. Not Fun at all. I carry an Epi-pen and benedryl is always close. It’s very frustrating when you realize that so much food contains onions in some form. I strongly suggest avoiding ANYTHING onion or in the Onion family. So far Garlic is OK

  9. I have noticed I get really bad headaches when I eat onion or onion products. Would Benedryl help me? Headaches was not listed as a allergic reaction to onions.

    1. Hi Lynn,
      Yes, in answer to your question about headaches. So far in all that I have read there are really and truly terrible side effects to an onion allergy. Keep looking things up online and doing research…. but yes, headaches are a real issue. Good luck.

  10. oh the infamous onion allergy. Developed it about 4-5 years ago. Totally avoid Mexican restaurants as they use the same cutting surfaces, knives, etc for everything that they use for onions. I never get “food mixtures” any kind when eating outside my home, strictly meat, veggies, no sauce, oil and vinegar on salad, etc. I find that if you make it crystal clear they will be calling 911 if you get any onion the chef will be out to speak with you. Always take something you know you can eat to a dinner or picnic, just to be sure. It is a pain in the butt but much better than the allergy symptoms and the risk. My husband is an excellent cook (who loves onions) but makes great meals for me without the deadly little buggers!

  11. I love onions and have never had a problem with them until I started getting reactions from them starting about a year ago ( 2012-2013 ) . The sinus area between my eyes and nose , and my nose itself gets swollen . It also cause me to break out , and it only takes a little bit of onion . It started out being the ” raw cooking onions ” that would give me reactions , but now it seems most onions do it now however I still seem to be ok with green onions , ” for now ” . This just started all of a sudden , like I said , around a year ago . Personally I don’t believe you can just all of a sudden develop an allergy to something you have been eating for almost fifty years . There has to be something different about the onions themselves and I’m willing to bet it has something to do with genetic modifications . I love onion on almost everything but now it seems that I have to stay away from them ” either that or walk around looking like the elephant man for three or four days . Pretty soon everyone will be allergic to water .

    1. Same for me! I got allergic to something and discover couple of days ago was onion! I got 3 major crisis in bed for 24 hours! I was poisoned with something… I still don’t know from now if I’m allergic to other stuff… But everything is good in my stomach right now. Thanks for your comments everyone.

  12. Just started to pinpoint onions as a source for my gastritis symptoms and have also noticed when I eliminate them the arthritis I have in a couple of fingers lessens. I have always loved onions and when I was a kid I would pull them out of the garden and munch happily away, but as I get older I seem to have to eliminate more from my diet to avoid stomach aches. It’s interesting that onions are part of the lily family and about 10 years ago my favorite face cream became “new and improved” which caused me to break out in hives. I compared the new ingredients to the old and the only new ingredient was a type of lily root. I will be trying to avoid the lily family for a while to see how it affect my symptoms.

  13. My friend is allergic to onions, and she is supposed to keep and epi-pen on her as she has really bad reactions to it! However a while ago she ate a crisp without thinking and it turned out it had onion in it and she never had a reaction! We’re going on holiday soon & she has made an appointment with an allergist to see if she is still allergic to them. Is it possible to become unallergic to onions, garlic etc? She’s only 17 and I’m not sure when she found out so we are hopeful that she can start a normal life soon!

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  16. After eating 4 grilled onions a day for 5 days in a row last week (yep, I went onion crazy thanks to my visiting brother showing off his mad grilling skills), I ended up with 20 epi shots to date, a steroid (Medrol/biacin) 4-day treatment, and a painful Santa Clause like stomach that is keeping me up right now!

    I’m allergic to many, many meds, but have never had a food allergy (I thought). Onions have never been my friend, but, wow, those suckers tried to kill me last week (with my help).

    Thanks for this site. I now know I’m not crazy and have an idea of what to expect in my new onion-free world. Lots of epinephrine! Onions are everywhere! … I live with epinephrine at home in a vial and needles bc my medicine allergies are nuts, but I’m going to have to invest some money into epi-pen stock bc how can I ever eat out again without mega panic?

    Oh, and this bloating and pain and throat-closing has been going on since last Sunday. I can’t seem to get this allergin out of my body! (Then again, I ate like 4 to 5 a day.)

    Thanks for listening, my fellow sufferers. … Did the minimal Cowboy Girl ranch dressing at dinner tonight f me up? .,. I’m just not good at this. … Throat’s getting tight. Gotta run …

  17. Eating out is a pain. Have to make sure you say no onions, garlic or scallions and that server and cook understand scallions ARE onions. You try to be subtle but sometimes no matter what you say, you get onions or the manager overreacted and brings out the chef (this is more likely in a seafood restaurant where they deal with shellfish allergies). I hate drama especially if I just want a quiet night out. I generally try to order something simple where the onion and garlic can easily be left out. I recently found an ITALIIAN restaurant that builds pasta from scratch and I can get pasta, plain olive oil, lemon artichoke black olives and shrimp. I just salt and pepper it myself. At home I make something similar with lime infused olive oil.

  18. I carry children’s fast melt benadryl for when I am not quite sure what is in what I am eating or I accidentally eat something with onions or garlicn

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  21. I am wondering if there is a correlation to people who take too many anti-hystimines/ steroids and then develop such allergies. My partner suffers violently from onion and Garlic allergy, he was able to eat them both till age 30, then instantly changed to allergic with vomiting, high blood pressure, headache etc. he has always suffered hay-fever, asthma, resulting in heavy use of particularly anti-hystime tablets, but also puffer steroids and cream steroids.

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