October 2025 |   ✓ Medically Reviewed by: Gary Falcetano, PA-C, AE-C 

You never had a problem with lobster before, but now if 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 never had childhood food allergies it can be confusing to experience these symptoms in adulthood, but the onset of food allergies in our adult years (adult-onset allergies) happens more often than you may think. It’s estimated that one in every 10 adults in the United States has a food allergy, and at least 12 million adults developed a food allergy as an adult.¹

Since food allergy symptoms can overlap with symptoms from other conditions, it can be tough to get to the bottom of what’s causing your particular symptoms. The first step is to understand what food allergies are and how they develop in adults. 

Common Food Allergies in Adults: Understanding the Causes

A food allergy happens when our body has an immune system response to a harmless substance.² There are proteins in foods that can cause these responses, and the most common foods that trigger an allergic response are: milk, eggs, peanut, tree nuts, soy, wheat, fish, shellfish and sesame.² Together, they’re known as the “Big 9” because they are responsible for 90% of all food allergies.³

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

Immune system changes

A person's immune system changes as they age. The aging process impacts the body at the molecular, cellular, and systemic levels.⁴ These immune system changes can lead to increased susceptibility to conditions like autoimmune diseases and allergies.⁴ So it might be that you previously ate peanut butter frequently when you were younger, but your immune system has changed. When you eat that peanut butter now, your body responds by creating IgE antibodies and that causes an immune reaction that results in food allergy symptoms.⁵

More sophisticated palate

There's a very good chance that there are foods you like as an adult that you either weren't exposed to as a kid or just didn't like them when you were younger. Maybe as a kid your family never really ate any sort of seafood, but as an adult you've realized you really enjoy lobster and shrimp. However, every time you eat lobster, you break out in hives. That could mean you have a shellfish allergy. It also could mean that you've had that allergy your entire life, you just didn't know it because you didn't eat lobster previously.

Tick bite troubles

If you've noticed that you've started to experience reactions after eating red meat, and have been bitten a tick, you might have alpha-Gal syndrome. When a tick feasts 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 lived in Florida for most of your life, but move to Ohio, you are going to be exposed to very different plant life. You will likely see different trees, grasses, and weeds (and their pollen). There's a chance that you might start to experience seasonal allergy symptoms that you never had before. And those allergic rhinitis symptoms might not show up right away. You may need to experience a few pollen seasons to become fully sensitized and develop symptoms.

What does pollen have to do with food allergies? Sometimes a non-food substance can trigger an allergic response, such as pollen from a plant. It's usually referred to as oral allergy syndrome of pollen food allergy syndrome. Our bodies create antibodies to that pollen — the allergic response — and if we eat something with similar-shaped proteins, our antibodies will react to that food protein and have an allergic response to it, too.⁶

For example, someone may have an allergy to birch pollen and then find that they also have a reaction when eating apples. This is because the major allergic trigger in apples is similar to the triggering protein in birch tree pollen.⁷ This situation is called “cross-reactivity” and it can complicate the picture around food allergies.

How Food Allergies Are Diagnosed in Adults

One reason why food allergies can be challenging to diagnose is because there are many types of symptoms that may present themselves. Symptoms of a food allergy can impact 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 all the way to life-threatening anaphylaxis.³ In rare cases, ingesting a food you’re allergic to and then working out can lead to exercise-induced anaphylaxis.³ The potential severity of food allergies makes it vital to find out what is causing your symptoms so you can avoid your particular 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 furthers the 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 be due to metabolic issues, an autoimmune condition, 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 when and how your symptoms occur.⁸ Your primary care provider can order these tests or refer you to a specialist to conduct an evaluation. Specific IgE blood testing can help identify which specific food you're sensitized to and can take it a step further by identifying the specific allergen component of that food you're reacting to.⁹ This helps determine if you’re at risk of a severe allergic reaction.⁹

Testing with allergen components also helps identify if you can tolerate a heated version of your trigger, such as egg or milk that’s been baked in a cake.⁹ And testing with allergen components can evaluate if a reaction is due to cross-reactivity, like the birch pollen and apple example described earlier.⁹ All of this information is crucial to understanding your risk levels and what is at the root cause of your symptoms.

How to manage food allergies

Once you know you have a food allergy, there are steps you can take to manage your symptoms. The most important step is to avoid your allergic triggers in the first place — but this requires some diligence, especially when you’re not eating at home. 

Always read food labels to make sure your triggers aren’t included.³ If you’re eating someone else’s cooking or you’re 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.³ If you have an allergy to milk or eggs even in their cooked form, be sure to ask about the use of butter or eggs in sweets, frostings and sauces.³

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).³ Keeping some antihistamines with you when you go out to eat can be sufficient if your symptoms and risk levels are mild.³ Be sure to discuss your individual level of risk with your healthcare provider to allow for 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

Millions of adults in the U.S. are living with food allergies.¹ Nearly 11% of adults have at least one food allergy, and about a quarter of those who have been diagnosed have also been prescribed epinephrine.¹ But, studies show that many people who need epinephrine may not have had it prescribed¹, and because of the risk of severe reactions, those who suspect they have a food allergy should discuss their symptoms with their healthcare provider.

By combining medical history and examinations with specific IgE blood testing, you and your provider can get to the bottom of your symptoms and determine if you have a food allergy, which in turn can help your provider create a personalized management plan for you. The full picture of your symptoms and risk levels means you can avoid those food allergens that trigger symptoms and still be able to safely enjoy going out to eat. Understanding your allergic triggers empowers you to feel better and can improve your quality of life.