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Allergies to Onions

By Elizabeth Wolfenden

Although the specific allergen may vary, allergies to different foods are quite similar. All food allergies, including an allergy to onions, may produce the same set of symptoms and be treated by the same lifestyle modifications or medications. However, it's important to know specifically which food is causing the allergic reaction so people can take the appropriate steps to avoid their exposure to this food. People who believe they have an onion allergy should consult an allergist for confirmation of the allergy and discuss specific treatment options.


Symptoms of an allergy to onions are the same as any other food allergy. They include nausea, vomiting, diarrhea, stomach cramps, hives, redness or inflammation of the skin and swelling. Some people also experience itchy eyes or a runny nose.

Time Frame

Symptoms of an onion allergy may occur within minutes of eating or being exposed to an onion. However, some people may not experience symptoms until up to two hours after exposure to onions, according to the American Academy of Allergy, Asthma and Immunology.


The best treatment for an allergy to onions is to avoid them entirely, according to the American Academy of Allergy, Asthma and Immunology. However, if onion exposure is accidental or unavoidable, antihistamine medication or injectable epinephrine medication--sometimes referred to as an epi-pen--may prove beneficial. People with an onion allergy should always thoroughly explore all treatment options with their doctors or allergists.


Although a person with a food allergy should be cautious about what she eats, those with an onion allergy may need to be particularly conscientious about it. Onions are often used as one of many ingredients in a recipe, and their presence in a food may not always be obvious. People with an allergy to onions should always read the labels before eating processed foods or check with the cook before eating prepared meals to ensure their meal is onion-free.


Onions are not considered a major food allergen, according to the U.S. Food and Drug Administration, but this doesn’t mean they can’t be dangerous to someone with an onion allergy. Some people may develop a condition called anaphylaxis, which can be fatal. Symptoms of anaphylaxis vary but may include sudden swelling, difficulty breathing, rapid or uneven heartbeat, dizziness, lightheadedness or feeling faint, confusion and a loss of consciousness. People experiencing this condition need emergency medical attention.

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