Food Allergy: Reactions After Eating, Testing and When to Call 911

What it involves

MedlinePlus explains that a food allergy is an abnormal immune system reaction to certain foods, which the body mistakenly treats as harmful. The reaction is usually mild, but in some cases it can be serious or life-threatening, and a food intolerance is different because it is not an immune reaction.

Who this is for

• Patients who break out in hives, swell, or feel itchy after eating a particular food
• Patients unsure whether stomach upset after meals is an allergy or an intolerance
• Adults who developed a reaction to a food they used to eat without trouble
• Parents of children with eczema or asthma who worry about food reactions

What to expect

• Questions about what you ate, how soon symptoms began, and what happened each time
• A physical exam and a review of your other allergies, eczema, and asthma
• A plan for testing, which MedlinePlus says may include skin tests, blood tests, an elimination diet, or a supervised food challenge, often arranged with an allergist
• Guidance on avoiding the food, and a discussion of an emergency plan when a reaction could be severe

The foods behind most reactions

MedlinePlus says most food allergies are caused by cow's milk, chicken eggs, shellfish such as shrimp, crab, and lobster, fish, peanuts, sesame, soy, tree nuts such as almonds, walnuts, and pecans, and wheat. A person may be allergic to more than one food. Both children and adults can have food allergies, some children outgrow them, and adults can develop new ones.

Allergy or intolerance

MedlinePlus separates the two. A food intolerance also brings symptoms after eating, but they are typically digestive, such as bloating and gas, and it is not an immune reaction. The lactose intolerance guide covers the best-known example. Hives are covered in the hives guide, and itching without an obvious rash is covered in the itchy skin guide.

What a reaction looks like

MedlinePlus says symptoms usually start within a few minutes to two hours after eating the food and can include:

• Hives, flushed skin, or a rash
• Tingling or itching in the mouth, or swelling of the face, tongue, or lips
• Vomiting, diarrhea, or belly cramps
• Coughing, wheezing, dizziness, or lightheadedness
• Swelling of the throat and vocal cords, or trouble breathing

Anaphylaxis is an emergency

In rare cases a food allergy causes a life-threatening reaction called anaphylaxis, which MedlinePlus says can narrow the airways, cause severe trouble breathing, and drop blood pressure into shock, with loss of consciousness. It may start with milder symptoms and then worsen. MedlinePlus says to call 911 if someone has symptoms of anaphylaxis. Do not wait to see if it passes or drive yourself.

How food allergies are diagnosed

A provider asks about symptoms and family and medical history, does a physical exam, and arranges food allergy testing. MedlinePlus lists skin testing, blood testing, a food elimination diet, and an oral food challenge, and says the oral food challenge is the most accurate test. Because these tests can cause reactions or need special setups, they are usually done through an allergist. Allergies that affect breathing are also covered in the seasonal allergies guide.

Living with a food allergy

There is no cure, according to MedlinePlus, and the only way to prevent a reaction is to avoid the food. Antihistamines and corticosteroids can reduce symptoms, and a provider may prescribe an epinephrine auto-injector to treat anaphylaxis. If you are prescribed one, learn to use it and carry it with you at all times. MedlinePlus also suggests a medical alert bracelet that names your allergy, and read labels every time.

Sources

• MedlinePlus — Food Allergy
• MedlinePlus — Lactose Intolerance