You never had a problem with lobster before, but now, when you eat it, your face and tongue start to swell. Or, perhaps eating tree nuts wasn’t an issue when you were younger, yet now you break out in a rash after eating your favorite walnut brownies.

If you've never had childhood food allergies, it can be confusing to experience these symptoms in adulthood, but adult-onset food allergies occur more often than you might think, affecting up to 10% of adults.¹

Since food allergy symptoms can overlap with those of other conditions, it can be challenging to determine their cause. The first step is to understand what food allergies are and how they develop in adults.

Shellfish lined up in neat rows. Adults can develop shellfish allergy.

Common food allergies in adults: Understanding the causes

A food allergy occurs when our immune system reacts to a harmless substance.² There are proteins in foods that can trigger these responses, and the most common foods that cause allergic reactions are: milk, eggs, peanuts, tree nuts, soy, wheat, fish, shellfish, and sesame.²

You might not have had any sensitivity to these (or other) foods before, so why are you experiencing them now?

Immune system changes

A person's immune system changes as they age. The aging process affects the body at the molecular, cellular, and systemic levels.³ These changes in the immune system can make a person more prone to conditions like autoimmune diseases and allergies.³ So, it might be that you used to eat peanut butter frequently when you were younger, but your immune system has since changed. When you eat that peanut butter now, your body responds by producing IgE antibodies, which trigger an immune reaction that causes food allergy symptoms.⁴

More sophisticated palate

There's a good chance that some foods you enjoy as an adult are ones you either weren't exposed to as a child or simply didn't like when you were younger. Maybe your family never really ate any seafood when you were a kid, but now you've discovered that you really enjoy lobster and shrimp. However, every time you eat lobster, you break out in hives. That could indicate you have a shellfish allergy. It might also mean you've had that allergy your whole life; you just didn't realize it because you never ate lobster before.

Tick bite troubles

If you've noticed that you've started to have reactions after eating red meat and have been bitten by a tick, you might have alpha-Gal syndrome. When a tick feeds on a mammal, such as a deer, it ingests the alpha-Gal sugar molecule. If that tick then bites a human, it can transmit this molecule into the person’s bloodstream. This can then trigger an allergic reaction if the person eats any mammalian products.

A change in geography

If you move to a different region, you'll be exposed to very different plant life. You will likely see different trees, grasses, and weeds (and their pollen). There's a chance you could start experiencing seasonal allergy symptoms that you never had before. These allergic rhinitis symptoms might not appear immediately. You may need to go through a few pollen seasons to become fully sensitive and develop symptoms.

What does pollen have to do with food allergies? Sometimes, a non-food substance like pollen from a plant can trigger an allergic response. It's usually called oral allergy syndrome or pollen-food allergy syndrome. Our bodies produce antibodies to that pollen — the allergic response — and if we eat something with similar-shaped proteins, our antibodies will react to that food protein as well, causing an allergic response.⁵

For example, someone might have an allergy to birch pollen and then also react to eating apples. This is because the main allergic trigger in apples is similar to the protein that causes the reaction in birch tree pollen.⁶ This situation is called “cross-reactivity,” and it can make understanding food allergies more complicated.

How food allergies are diagnosed in adults

One reason why food allergies can be difficult to diagnose is that they can cause a wide range of symptoms. Symptoms of a food allergy can affect different parts of the body, including:

Skin: rashes, hives and/or itching
Respiratory system: itchy mouth, tongue or throat; swelling; wheezing or coughing; difficulty breathing
Gastrointestinal system: stomach cramps, diarrhea, nausea, vomiting, bloating

These symptoms can range from mild irritations to life-threatening anaphylaxis.⁷In rare cases, ingesting a food you’re allergic to and then working out can cause exercise-induced anaphylaxis.⁷The potential severity of food allergies makes it crucial to determine what is triggering your symptoms so you can avoid your specific risk factors.

Many of these common allergic symptoms overlap with non-allergic food-related symptoms, such as lactose intolerance, irritable bowel syndrome, or celiac disease, but the underlying causes are different.⁸ This overlap increases confusion and uncertainty around food allergy. As noted, a true IgE-mediated food allergy is an immune response to an allergic trigger. But a food intolerance isn’t caused by the immune system — it can result from metabolic issues or the creation of excess gas during digestion, among other causes.⁸

So, how can you rule allergies in or out? A specific IgE blood test is an important part of getting to an accurate diagnosis, along with your medical history and details about when and how your symptoms occur.⁸Your primary care provider can order these tests or refer you to a specialist for further evaluation. Specific IgE blood testing can identify which particular food you are sensitized to and can go further by helping to pinpoint the exact allergen component of that food that may be causing your reaction.⁹This helps assess if you’re at risk of a severe allergic reaction.⁹

Testing with allergen components also helps determine whether you can tolerate a heated version of your trigger, such as egg or milk baked into a cake.⁹ And testing with allergen components can assess whether a reaction is due to cross-reactivity, like the birch pollen and apple example mentioned earlier.⁹ All of this information is essential for understanding your risk levels and identifying the root cause of your symptoms.

How to manage food allergies

Once you know you have a food allergy, you can take steps to manage your symptoms. The most important step is to avoid your allergic triggers altogether — but this requires careful attention, especially when you’re not eating at home.

Always read food labels to ensure your triggers aren’t included.⁷ If you’re eating someone else’s cooking or dining at a restaurant, be sure to explain what you’re allergic to and ask about ingredients in sauces, salad dressings, and other parts of the meal.⁷ If you have an allergy to milk or eggs, even in cooked form, make sure to ask about the use of butter or eggs in sweets, frostings, and sauces.⁷

If you’re at risk for a life-threatening reaction like anaphylaxis, carry one or two epinephrine pens with you at all times (two is recommended in case the first one wears off quickly).⁷ Keeping some antihistamines with you when you go out to eat can be enough if your symptoms and risk levels are mild.⁷ Be sure to discuss your individual level of risk with your healthcare provider to develop a personalized allergy management plan.

Changing your diet to cut out foods that trigger your symptoms can be frustrating, but it may be necessary to keep you feeling better and prevent your symptoms from flaring up.

Living with food allergies

By combining medical history and examinations with specific IgE blood tests, you and your provider can identify the cause of your symptoms and determine if you have a food allergy. This information can help your provider develop a personalized management plan for you. Having the full picture of your symptoms and risk factors allows you to avoid those food allergens that trigger symptoms while still enjoying eating out safely. Understanding your allergic triggers gives you the power to feel better and can improve your quality of life.

Learn how to get tested for food allergies

References

Santos AF, et al. EAACI guidelines on the diagnosis of IgE-mediated food allergy. Allergy. 2023;78:3057-3076.
What is a food allergy? [Internet]. Food Allergy Research & Education [cited 2025 Oct 7]. Available from: https://www.foodallergy.org/resources/what-food-allergy.
De Martinis M, et al. Allergy and Aging: An Old/New Emerging Health Issue. Aging Dis. 2017;8(2):162-175.
Allergies and the Immune System [Internet]. Johns Hopkins Medicine. [cited 2025 Oct 7]. Available from: https://www.hopkinsmedicine.org/health/conditions-and-diseases/allergies-and-the-immune-system.
Migueres M, et al. Types of sensitization to aeroallergens: definitions, prevalences and impact on the diagnosis and treatment of allergic respiratory disease. Clin Transl Allergy. 2014;4:16.
Ciprandi G, et al. Birch allergy and oral allergy syndrome: The practical relevance of serum immunoglobulin E to Bet v 1. Allergy Asthma Proc. 2016;37(1):43-49.
Kurowski K, Boxer RW. Food allergies: detection and management. Am Fam Physician. 2008 Jun 15;77(12):1678-86.
Onyimba F, et al. Food Allergies and Intolerances: A Clinical Approach to the Diagnosis and Management of Adverse Reactions to Food. Clin Gastroenterol Hepatol. 2021;19(11):2230-2240.e1.
Canonica GW, et al. A WAO - ARIA - GA²LEN consensus document on molecular-based allergy diagnostics. World Allergy Organ J. 2013;6:1-17.

Resources for Medical Professionals

Resources for Medical Professionals

Adult-onset food allergies: Causes, symptoms and management

Common food allergies in adults: Understanding the causes

Immune system changes

More sophisticated palate

Tick bite troubles

A change in geography

How food allergies are diagnosed in adults

How to manage food allergies

Living with food allergies

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