Onion Allergy – Symptoms, Tests and Treatments

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Onion Allergy

Onion is a widely cultivated vegetable which is used in a lot of recipes. It is a species of genus “Allium“. But there are few people who have been suffering from allergic reaction as soon as they consume onion.

The reaction is mild in most occasions but can be severe if not treated seriously. This can turn out as deadly on rare occasions though. One can either have an allergy to cooked or raw onions.


Raw onion allergy has more converse effects as the protein exists in it. But upon cooking or frying, the protein departs it. So, a lot of people face no problem at all or very little reaction with cooked onions.

It is hard to find a recipe without onions as it brings a different taste in food. Sauce, ketchup, fast foods and salad are some of the food items which need onions in it. But if you are suffering from onion allergy, you should not smell or come in contact with it. If you are very sensitive, then even the vapor of onions can create some reaction in the body.

What Causes an Allergy to Onions?

The onion allergy causes in the same way as other food allergies. When you consume raw onions or a food which contain onions, the immune system of the body reacts negatively to it. The immune system of the body infers that the protein of this vegetable will harm the body.

To kill this protein, the immune system immediately releases antibodies such as IgE which comes in contact with the protein. The protein and IgE fights against each other and as a result Histamine is produced in the body or specifically from the gut or skin for the sake of safety of the body.

The chemical Histamine is produced in an excessive manner than necessity and reacts adversely to the body and this results onion allergy to trigger. The time to start reaction will significantly vary with patient’s sensitivity to this vegetable and the amount of consumption.

Usually, it can take up to a few minutes to a an hour to show its impact on the body. Sometime people can’t understand whether it is the allergy to onions or anything else. If you are unsure, avoid foods which contain onions for a few days and check out what is the outcome. If you are not having any reaction like you did earlier, then it is concluded that it was onions which was responsible for those irritating moments.

Onion Allergies or Intolerance?

The symptoms of allergy and intolerance are almost identical and it makes people confused to differentiate them. The onion allergy reacts very quickly. It can start within a minute after eating onions. The reaction can be very severe and life threatening. But with onion intolerance, it may take up to a day for the symptoms to appear and the reaction is mild.


Some people can’t tolerate the sulphur and chemical that onion has. So, when they ingest it, they feel discomfort and eventually experiences negative symptoms. They can’t digest it naturally in a particular day. Hives and sore on the mouth are the primary signs of onion intolerance. The other symptoms for onion intolerance are bloating, swelling on faces, stomach cramp, diarrhea etc.

The Symptoms of Onion Allergy to Detect it:

These are the symptoms found in most people who are having a reaction to onion. The best way is to diagnose it by conducting a medical test.

  • Anaphylaxis (rare)
  • Diarrhea
  • Eye irritation
  • Headache or Migraine
  • Itching on different parts of the body such as mouth, throat, lips etc.
  • Nausea
  • Shortness of breathing
  • Skin inflammation and red sign
  • Stomach cramps
  • Swelling and facial flushing on skin
  • Vomiting
  • Wheezing

Different Types of Tests to Conduct:

The test is the only way to assure whether you have been suffering from hypersensitivity to onion or not. This is undoubtedly not possible to be 100% confident about the allergy by looking at symptoms only. In the lab, the doctor will conduct an IgE blood test, which is so far the most effective way to detect it. In some case, you may be anticipating allergy, but after the test it may be found that it is just an intolerance.

So, onion allergy test is mandatory to be able to detect it with full evidence. If needed, the doctor might perform skin prick test, patch test, intradermal test in order to find out the substance or allergen.

Treatment and Prevention:

If you are allergic to onions, then avoid all foods which contain onions. The best option is to prevent it as it is not possible to cure onion allergy permanently. Stay in an environment where onions are not cultivated as to smell it or coming to its contact can start the reaction.

Always prefer onion free recipes and inform the cook about your problem in prior of attending in a party. In some restaurants, allergy free food items are available for onion allergy sufferers. If the reaction is very severe then there is no alternative of taking medications from doctors. The type of medicines will vary on the level of condition of the sufferer. You can always carry antihistamine with you and take it without any prior suggestion from a doctor. Some pharmacy doesn’t want the doctor’s prescription for providing antihistamine as this is a common way to prevent an allergy reaction.

If the reaction is severe or you get an anaphylactic shock then the epinephrine injection is mandatory for the sufferer. This saves the life of the patient by offering a quick relief. There are some tablets and ointments in the next door shops which should not be used unless doctor suggests it. You should always keep in contact with an allergist and maintain his advice in urgent moment.

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