Food allergy is an immune system reaction that occurs soon after eating a certain food. Even a tiny amount of the allergy-causing food can trigger signs and symptoms such as digestive problems, hives or swollen airways. In some people, a food allergy can cause severe symptoms or even a life-threatening reaction known as anaphylaxis.
Food allergy affects an estimated 6 to 8 percent of children under age 3 and up to 3 percent of adults. While there's no cure, some children outgrow their food allergy as they get older.
It's easy to confuse a food allergy with a much more common reaction known as food intolerance. While bothersome, food intolerance is a less serious condition that does not involve the immune system.
For some people, an allergic reaction to a particular food may be uncomfortable but not severe. For other people, an allergic food reaction can be frightening and even life-threatening. Food allergy symptoms usually develop within a few minutes to two hours after eating the offending food.
The most common food allergy signs and symptoms include:
• Tingling or itching in the mouthAnaphylaxis
• Hives, itching or eczema
• Swelling of the lips, face, tongue and throat or other parts of the body
• Wheezing, nasal congestion or trouble breathing
• Abdominal pain, diarrhea, nausea or vomiting
• Dizziness, lightheadedness or fainting
• Constriction and tightening of airwaysEmergency treatment is critical for anaphylaxis. Untreated, anaphylaxis can cause a coma or even death.
• A swollen throat or the sensation of a lump in your throat that makes it difficult to breathe
• Shock with a severe drop in blood pressure
• Rapid pulse
• Dizziness, lightheadedness or loss of consciousness
• milkMost children that have a food allergy will have experienced eczema during infancy. The worse the child's eczema and the earlier it started, the more likely they are to have a food allergy.
• tree nuts
• peanutsTypes of food allergies
• tree nuts – such as walnuts, brazil nuts, almonds and pistachios
• crustaceans (shellfish) – such as crab, lobster and prawns
Food allergies are divided into three types, depending on symptoms and when they occur.
o IgE-mediated food allergy – the most common type, triggered by the immune system producing an antibody called immunoglobulin E (IgE). Symptoms occur a few seconds or minutes after eating. There is a greater risk of anaphylaxis with this type of allergy.
o non-IgE-mediated food allergy – these allergic reactions are not caused by immunoglobulin E, but by other cells in the immune system. This type of allergy is often difficult to diagnose as symptoms take much longer to develop (up to several hours).
o mixed IgE and non-IgE-mediated food allergies – some people may experience symptoms from both types