Food Allergies

What Is a Food Allergy?

A food allergy is an immune system reaction to normally harmless proteins in foods. This response of the body’s defense system can range from mild to severe.

Food allergies are more common in children than adults. Although some youngsters outgrow their allergy to milk, soy, wheat, and eggs, allergies to peanuts (a legume), tree nuts (almonds, cashews, pecans, hazel nuts, pistachios, pine nuts, walnuts), fish, and shellfish tend to persist.

Jump to a video about food allergy challenge preparation

Some children have both asthma and food allergies. When this happens, the symptoms frequently are more severe.

People who have hay fever, which is triggered by pollen, may also have pollen-food allergy syndrome. Certain uncooked fruits and vegetables or nuts and spices can prompt symptoms including mouth tingling or itch, swelling of the lips, mouth or tongue. Rarely, swelling of the throat or even a life-threatening condition called anaphylaxis can occur.

Food Protein-Induced Enterocolitis Syndrome (FPIES), most often seen in infants, is a delayed-onset food allergy affecting the gastrointestinal tract. Severe vomiting, diarrhea, and resulting dehydration can occur beginning two to six hours after consuming milk, soy, certain grains and some other foods, often after the child encounters them for the first time. Because the symptoms resemble those of a viral illness or bacterial infection, a diagnosis of FPIES may not be immediate. If these symptoms arise after the infant tries a new food, parents should bring him or her to the emergency department for treatment.

What’s the Difference Between Food Intolerance and Food Allergy?

The symptoms of food intolerance can be the same as those of a food allergy: nausea, vomiting, diarrhea, and so on, and thus may be difficult to distinguish. Typically, people who have intolerance can eat small amounts of troublesome foods without ill effects; those who are allergic cannot.

Some of the offenders that can cause a reaction that mimics a food allergy are food poisoning, lactose intolerance, additives such as sulfites in wine, histamine toxicity from fish that isn’t refrigerated properly, and celiac disease, which is related to gluten intolerance.

What Causes a Food Allergy?

The body’s immune system mistakenly perceives a substance in food as harmful. It triggers the release of an antibody called immunoglobulin as an antidote to the allergen.

When the allergic person next consumes the troublesome food, the antibodies react by calling for the body to release histamine and other chemicals that cause allergy symptoms.

What Are the Signs and Symptoms of a Food Allergy?

The immune system signals the body to release histamines and other chemicals, which can cause:

• Abdominal pain, nausea, vomiting, or diarrhea.
• Itchy hives.
• Swelling of the lips, tongue, or throat that may make breathing difficult.
• Coughing or wheezing.
• Nasal congestion.
• Dizziness or fainting.
• A life-threatening allergic reaction called anaphylaxis.

Symptoms can come on within minutes of eating the problem food, or within a few hours later.

How Is a Food Allergy Diagnosed?

A skin scratch test, a simple procedure in the allergist’s office, can be used to confirm food allergies and identify the specific triggers. The skin is exposed to an allergen through a tiny puncture or scratch. The area is observed for a reaction, such as a small hive (raised, reddened, itchy blotch). The test can confirm whether the patient reacts to something they breathe, touch, or eat.

An oral challenge also may be used to check for allergies to food. Beginning with a small amount of the food that has triggered an allergic reaction, the patient gradually receives larger amounts while being closely monitored in the doctor’s office.

What Can I Do About a Food Allergy?

Some steps you can take for your child:

• Read food labels to protect your child from known triggers.
• Be especially wary of food in restaurants that may include ingredients you don’t expect.
• Keep a diary of what your child eats and note which foods spark symptoms.
• Talk with the school nurse about your child’s medical needs.
• Have your child wear a medical alert bracelet.
• Let the school nurse and other staff, team coaches, day care workers, and other adults know about your child’s food allergy and what to do in case of an attack.
• If your child has severe reactions, ask your physician whether an emergency epinephrine injector is needed.

What Treatment Is Available for Food Allergy?

Minor (involving a single organ) reactions can be treated with over-the-counter or prescribed antihistamines to relieve itching and hives.

Severe reactions require an emergency epinephrine injection and a visit to the nearest emergency department.

Hasbro Children’s has a Food Allergy Center where you can get help.

Learn about treatment at Brown University Health for more pediatric asthma and allergy conditions