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Seasoning your food with savory ingredients such as garlic, onions, shallots, and leeks can deliver great flavor. But for some people, eating these vegetables, which belong to a family called alliums, can lead to uncomfortable or even dangerous reactions.
Keep reading to learn what an allium allergy is, symptoms to look for, and how this condition is managed.
Alliums are vegetables grown from bulbs that many people add to foods for their bold flavors. Vegetables in the allium family include:
Allergies to onion, garlic, and other alliums are uncommon, but they do occur. An allergy to one type of allium often extends to other members of the allium family due to their similar protein structures. Some people are allergic to one or two alliums, while others may not be able to eat any of them.
“Anyone else have garlic and onion allergies?” one MyFoodAllergyTeam member asked. Another replied, “Yes, but only to onions. I have loved onions all my life, but a couple years ago it started with diarrhea and now I can’t eat them at all, not even dried ones. And I’ve discovered that onions are in almost everything.”
If you’ve noticed that you have reactions to one type of allium, talk to your primary care provider or an allergist. They can figure out which alliums cause you to have a reaction.
While uncommon, it’s possible to have an allium allergy. Many people who have reactions to alliums may actually have an intolerance rather than a true allergy.
All alliums contain sulfur compounds, mainly allicin, that are released only when the plant is damaged. For instance, onions release chemical irritants when you cut them. This can cause watery eyes, nasal congestion, or skin irritation, which some people mistake for allergy symptoms. But other compounds in alliums may cause a true allergic reaction. For instance, one of the major allergens in onions is called alliin lyase.
Having an adverse reaction to eating alliums doesn’t necessarily mean you have a food allergy. You might have a food intolerance, also called a food sensitivity. While both allergies and intolerances can cause distressing symptoms, they have different causes and treatments.
An allium allergy is an immune system response. When someone with an allium allergy eats onion, garlic, or another allergen, their immune system reacts as if the food were harmful. Existing antibodies bind to the allergen, triggering the release of histamine and other chemicals to fight it off. As a result, people can experience allergy symptoms such as trouble breathing or itchiness.
On the other hand, an allium intolerance, or allium sensitivity, is a nonimmune reaction. It can inhibit the body’s ability to digest certain foods properly. Intolerances tend to be more common and less severe than allergies. Common symptoms include bloating, stomach pain, and gas.
True allium allergies are uncommon, and it’s hard to know just how often they occur because they’re not reported very often.
One study published in 2020 found that out of 8,109 people who visited an allergy clinic, roughly 11 percent were hypersensitive to food. While 17 people were sensitive to garlic and 10 people were sensitive to onions, that still made up less than 1 percent of the study population.
Another, older study aimed to measure the allergy potential for garlic and onions. Among 108 people, only 15 had a reaction to garlic and onions. Just one person had an onion-only allergy.
No large studies have evaluated the prevalence of other allium allergies, but researchers have said that allergies to leeks and chives are quite rare.
The symptoms of an allium allergy can range from mild to severe. They typically appear within minutes after exposure to the allium ingredient. Common symptoms include:
Some people may experience an allergic reaction just by inhaling allium vapors or touching an allium. For instance, you may tear up while cutting an onion or have a reaction by touching a cutting board where someone chopped garlic.
In rare cases, an allium allergy can lead to anaphylaxis. This is a severe and potentially life-threatening allergic reaction that requires immediate medical attention. People who have an anaphylactic reaction to alliums should carry an epinephrine auto-injector.
Diagnosing an allium allergy typically involves several steps. Your doctor or allergist will often begin with a detailed discussion of your medical history, including your symptoms, their timing, and potential triggers.
Your doctor may recommend an elimination diet, in which you avoid eating all alliums for a period of time. They may have you gradually reintroduce one or two allium ingredients over time and note any reactions in a food diary. If your symptoms flare when eating a specific allium, they’re most likely caused by that vegetable.
Your doctor may want to confirm your allergy with food allergy testing. If approved by your doctor, you could also experiment with different preparation methods. Some people have found that they can tolerate small amounts of cooked onions, for example, but not raw ones.
Skin prick tests can also test for allium allergies, with results usually in about 15 to 20 minutes. In a skin prick test, a healthcare professional applies the suspected allergen to your skin. This is usually on your arm or back, using a sterile needle or probe. If your skin becomes raised and itchy, like a mosquito bite, you may have an allergy.
A blood test can measure the levels of specific immunoglobulin E (IgE) antibodies to allium proteins. You can typically expect results back within a week or two.
Another possible diagnosis method is an oral food challenge. Under medical supervision, you eat increasing amounts of alliums at your allergist’s office so they can observe any allergic reactions. Your allergist can administer medical treatment if necessary. Don’t try an oral food challenge at home without proper medical supervision.
The primary management strategy for both allium allergy and intolerance is avoidance. This involves carefully reading food labels and being cautious when eating out. Onions, garlic, scallions, and powders made from these alliums are common ingredients in many dishes and processed foods.
When it comes to dining out, one MyFoodAllergyTeam member recommends researching common ingredients in dishes beforehand. “It isn’t always enough to avoid a reaction, but it helps me to stay away from general dishes that will never, and can never, be safe, no matter how much I want it,” they said.
Another member said it’s helpful to visit restaurants where you know that the staff takes food allergies seriously. “My solution is to frequent the same restaurant and call to make sure the servers we like and trust are working.”
Make sure all bowls, pans, and surfaces have been thoroughly cleaned after someone has had alliums on them. Several MyFoodAllergyTeam members have shared experiences where onions, garlic, or chives have been cut on the same surfaces or slicers as their food, causing adverse reactions.
The U.S. Food and Drug Administration (FDA) doesn’t require alliums to be listed as an allergen on food labels, so carefully examine ingredient lists. It’s common to find traces of alliums in salsas, broths, flavoring packets, and premade sauces and soups. Also, be careful when a food label lists “spices” as an ingredient, since it’s not always clear what that includes.
If you eat onions, garlic, or other alliums and have symptoms, your doctor may recommend antihistamines to reduce allergy symptoms. Sometimes, inhalers can help with breathing.
If you have an allium allergy, always carry an epinephrine auto-injector for emergency treatment of severe reactions. These can be prescribed by your doctor.
With both allium allergies and intolerances, it’s important to find substitutes to maintain a balanced diet, especially when cooking. You can try replacing onions or garlic with vegetables like celery, carrots, or fennel. You can also try herbs such as thyme, sage, or tarragon.
If you’re concerned about an allium allergy or intolerance, talk to your doctor. If you don’t already have an allergist, they may refer you to one for allergy testing and guidance for developing an allergy treatment plan.
On MyFoodAllergyTeam, people share their experiences with food allergies, get advice, and find support from others who understand.
How do you ensure you don’t consume alliums that might trigger a reaction? Let others know in the comments below.
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