Could you have a food allergy and not know it?

You’ve eaten shrimp in the past without any problems. But this time you develop a weird rash. Or maybe you have a stomachache. You always assumed food allergies were for kids. But could you become allergic to a food such as shrimp as a grown-up? You definitely can. New food allergies can develop at any time.

About 11% of American adults have a food allergy, according to a large 2019 survey published in the journal JAMA Network Open. Some of those allergies are ones they’ve had since childhood. But nearly half of those people developed at least 1 food allergy as adults. Here’s what causes these reactions in adults and how you can treat them.

Food allergy basics

For starters, it helps to know some basics. A food allergy happens when your body’s immune system sees a certain food as harmful. It responds by sending “defenders” to attack proteins in the food. Your body also releases substances called histamines, which cause symptoms such as hives, itchy skin and stomach pain.

Which foods tend to cause food allergies?

Shellfish is the top food allergen in adults, per data from the JAMA Network Open study. The most common foods that adults are allergic to include:

• Shellfish (crab, shrimp and lobster)
• Peanuts
• Tree nuts (such as almonds, walnuts, pecans, cashews and pistachios)
• Fish (bass, cod and flounder)
• Eggs
• Cow’s milk
• Soy
• Sesame seeds
• Wheat

If you have an allergy to any of these foods, the recommendation is to avoid eating them, says Payel Gupta, MD. She’s an allergy and asthma specialist and a clinical instructor at Mount Sinai Hospital in New York City.

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Symptoms of a food allergy

Sometimes food allergy symptoms are mild. At other times they can be more severe and result in a serious allergic reaction called anaphylaxis, explains Melanie Carver of the Asthma and Allergy Foundation of America.

Common food allergy symptoms include:

• Tingling or itching in the mouth
• Hives, itching or rash
• Swelling of the lips, face, tongue and throat
• Wheezing, runny nose or trouble breathing
• Abdominal pain, diarrhea, nausea or vomiting
• Dizziness, lightheadedness or fainting

Signs of anaphylaxis usually involve more than one part of the body, such as the skin or mouth, the lungs, heart and gut. These symptoms can be the same as with an allergic reaction. But they can be more severe, with several occurring at the same time. Other symptoms include:

• Shock with a severe drop in blood pressure
• Rapid pulse
• Uterine cramps
• Feeling that something awful is about to happen

It’s important to know that food allergy symptoms may change over time and vary with each allergic reaction, according to Food Allergy Research and Education (FARE). For example, you may have a little stomach pain when you eat eggs. But the next time you have them, you might have trouble breathing.

What to do if you suspect a food allergy

For a milder reaction to a food, such as a minor rash, don’t panic. Write down what you ate, what your symptoms were and how soon after eating you experienced the symptoms. Obviously, you’ll also want to steer clear of that food until you’ve seen your health care provider.

Ask your doctor about getting a referral to an allergist. “Talking about your reaction and why you think you might be allergic can help the allergist determine if you need testing,” Dr. Gupta says.

Testing can help determine whether you’re truly allergic to a food, says Dr. Gupta. Your doctor may do a skin-prick test or a blood test. “If it’s negative, the doctor may suggest an in-office food challenge to make sure you can truly tolerate the food,” she says.

A severe reaction that makes your throat swell or makes it hard to breathe is an emergency. If you’ve never been diagnosed with a food allergy and don’t have epinephrine (a rescue medication), you should get immediate medical help.

Treating an allergic reaction to a food

If you’re diagnosed with a food allergy, your doctor will prescribe a self-injectable medication called epinephrine, known as an EpiPen. This is the only treatment that stops a severe allergic reaction. You’ll need to carry the pen with you at all times. “If you accidentally get exposed to the food, epinephrine can help stop a reaction and save your life,” says Dr. Gupta.

Your doctor will help you create a food allergy treatment plan based on the symptoms you experience. They will probably recommend keeping an over-the-counter antihistamine (such as Benadryl^®) with you in case you have a single-symptom reaction. These medications can help with mild symptoms associated with an exposure to food. (Stock up on OTC antihistamines at the Optum Store and have them delivered directly to your door.)

“If you’re exposed to a food you’re allergic to, we cannot predict whether you’ll have a severe or mild reaction,” says Dr. Gupta. Being prepared is key.

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Additional sources
Adult allergy statistics: JAMA Network Open (2019). “Prevalence and Severity of Food Allergies Among US Adults”
Food allergy basics: Mayo Clinic (n.d.). “Food Allergy”
Symptoms: Food Allergy Research and Education (n.d.): “Food Allergy Essentials”
Testing: American College of Allergy, Asthma and Immunology (n.d.). “Food Allergy Testing and Diagnosis”