A food allergy is an adverse or abnormal reaction to a food or a food additive.

A few specific foods seem to cause a majority of the food reactions. The most common triggers of a food reaction include:

• Cow's milk
• Eggs
• Peanuts
• Wheat
• Soy
• Fish
• Shellfish
• Tree nuts (eg, walnuts, pecans)
• Sesame

Factors that increase your chance of food allergies include:

• Age: young children
• History of eczema
• History of other types of allergies, including hay fever

Symptoms include:

• Gurgling stomach
• Stomach cramps, pain
• Nausea
• Vomiting
• Diarrhea
• Skin rash, especially hives
• Skin itching
• Cough
• Wheezing
• Shortness of breath
• Swelling in lips, mouth, tongue, throat
• Nasal congestion
• Severe drop in blood pressure

The doctor will ask about your symptoms and medical history. A physical exam will be done. Food allergies are often diagnosed based on your own observations. It is a good idea to keep a diary of your symptoms. Note when the symptoms occur and what you have eaten.

Tests may include:

You may be asked to go on an elimination diet . This should be done under your doctor's care. You will not eat a suspected food. If your symptoms decrease or go away, your doctor can almost always make a diagnosis. If you eat the food and your symptoms come back, the diagnosis is confirmed. This method should not be used if symptoms are severe. It is most often only done in cases of atopic dermatitis . These are skin irritation issues. This test is uncommon in cases with anaphylactic symptoms. These include wheezing, shortness of breath and drop in blood pressure.

Your doctor can also use a scratch skin test. The doctor will dilute an extract of the food. The dilution will be placed on your forearm or back skin. The skin is scratched with a small pick or tiny needles. If there is swelling or redness, an allergic reaction may be present. The doctor will make the diagnosis based on the skin test and your history of symptoms. Some skin tests can have a severe allergic reaction. This test should only be used under the supervision of a physician or other trained medical personnel. Severe eczema may make this test hard to interpret.

The doctor may order blood tests (RAST or ELISA). These tests measure the level of food-specific IgE in the blood. IgE is a type of protein that the body produces when it comes in contact with something to which it is allergic. The presence of IgE in the blood may indicate an allergy.

Avoid foods and food ingredients that cause you to have an allergic reaction. If you think you've eaten something to which you are allergic, and you have difficulty breathing, call for emergency medical help.

Treatments include:

• Antihistamine medication—to decrease swelling and itching
• Epinephrine —injected immediately in the event of a severe, life-threatening reaction (anaphylaxis)
• Corticosteroid medication—for more severe swelling and itching

If you are diagnosed with a food allergy, follow your doctor's instructions .