Food Allergy: Symptoms, Causes & Treatment

Food allergy can cause symptoms like itchy skin, redness, raised swollen patches, or swelling of the lips. Some people also get a stuffy, runny nose, diarrhea, or constipation after eating certain foods or drinking certain beverages.

Most of the time, food allergy symptoms are mild and improve within a few hours after using the medication recommended by a healthcare provider. Still, reactions can sometimes be severe.

If you develop shortness of breath or trouble breathing, the situation can be life-threatening and you should seek emergency medical care right away. It’s also important to identify which food triggers your allergy so you can avoid it and reduce the risk of serious complications.

Common symptoms

The main symptoms of food allergy are:

• Itchy skin;

• Redness of the skin;

• Red, swollen patches on the skin;

• Swelling of the lips, tongue, ears, or eyes;

• Canker sores;

• Stuffy and runny nose;

• A feeling of discomfort in the throat;

• Abdominal pain and excess gas;

• Diarrhea or constipation;

• Burning or stinging when having a bowel movement.

Food allergy symptoms can start within minutes or a few hours after consuming the food, beverage, or food additive that triggers an inflammatory reaction in the body, and they can vary from person to person.

In some cases, people may also experience gastrointestinal (GI) symptoms such as nausea, vomiting, or abdominal discomfort. The respiratory system can also be affected, causing difficulty breathing or shortness of breath. This severe reaction is called anaphylactic shock.

Confirming a diagnosis

A food allergy should first be assessed by an allergist, who will evaluate the symptoms reported after eating a specific food. To confirm the exact cause, the allergist may recommend a skin test or a blood test.

A skin allergy test involves applying small amounts of different food extracts that are known to trigger allergies and then watching for a skin reaction over about 24 to 48 hours. After that period, the doctor will determine whether the test is positive or negative by checking for signs like redness, hives, itching, or blisters.

For blood allergy testing (specific IgE tests like ImmunoCAP), a small blood sample detects IgE antibodies to specific foods. These help assess allergy risk alongside symptoms and history, but an oral food challenge may still be needed for confirmation.

According to the National Institute of Allergy and Infectious Diseases (NIAID), the gold standard for diagnosing food allergy is an oral food challenge performed under medical supervision.

Main causes

Food allergy can be triggered by any substance found in a food or food additive, and it is more common in people with a family history of allergies.

Although any food can cause a reaction, food allergy symptoms are most often linked to seafood, peanuts, cow’s milk, soy, and tree nuts, for example.

Food allergy vs food intolerance

The main difference between food allergy and food intolerance is how the body responds to a specific food. With food allergy, an inflammatory reaction can develop within minutes after exposure to substances in the food, so symptoms tend to appear quickly and may be more widespread.

With food intolerance, symptoms are related to changes in how the food is digested, leading mainly to gastrointestinal symptoms.

Treatment options

Food allergy treatment depends on how severe the symptoms are, and this can vary from person to person. In general, healthcare providers may recommend antihistamines such as fexofenadine (Allegra) or loratadine, or corticosteroids such as betamethasone to help relieve and treat allergy symptoms.

According to the Centers for Disease Control and Prevention (CDC), epinephrine is the first-line treatment for anaphylaxis. An oxygen mask may also be needed to help with breathing.