More than 70 million UK citizens and Americans have an allergy of some kind. Food allergies are estimated to affect 4 to 6 percent of children and 4 percent of adults, according to the Centers for Disease Control and Prevention.
Food allergy symptoms are most common in babies and children, but they can appear at any age. You can even develop an allergy to foods you have eaten for years with no problems. Learn more about the types of food allergies.
The body’s immune system keeps you healthy by fighting off infections and other dangers to good health. A food allergy reaction occurs when your immune system overreacts to a food or a substance in a food, identifying it as a danger and triggering a protective response.
While allergies tend to run in families, it is impossible to predict whether a child will inherit a parent’s food allergy or whether siblings will have a similar condition. Some research does suggest that the younger siblings of a child with a peanut allergy will also be allergic to peanuts.
Symptoms of a food allergy can range from mild to severe. Just because an initial reaction causes few problems doesn’t mean that all reactions will be similar; a food that triggered only mild symptoms on one occasion may cause more severe symptoms at another time.
The most severe allergic reaction is anaphylaxis — a life-threatening whole-body allergic reaction that can impair your breathing, cause a dramatic drop in your blood pressure and affect your heart rate. Anaphylaxis can come on within minutes of exposure to the trigger food. It can be fatal and must be treated promptly with an injection of epinephrine (adrenaline).
While any food can cause an adverse reaction, eight types of food account for about 90 percent of all reactions:
Certain seeds, including sesame and mustard seeds (the main ingredient in the condiment mustard), also are common food allergy triggers and considered a major allergen in some countries.
Symptoms of an allergic reaction may involve the skin, the gastrointestinal tract, the cardiovascular system and the respiratory tract. They can surface in one or more of the following ways:
Vomiting and/or stomach cramps
Shortness of breath
Shock or circulatory collapse
Tight, hoarse throat; trouble swallowing
Swelling of the tongue, affecting the ability to talk or breathe
Pale or blue coloring of skin
Dizziness or feeling faint
Anaphylaxis, a potentially life-threatening reaction that can impair breathing and send the body into shock; reactions may simultaneously affect different parts of the body (for example, a stomachache accompanied by a rash)
Most food-related symptoms occur within two hours of ingestion; often they start within minutes. In some very rare cases, the reaction may be delayed by four to six hours or even longer. Delayed reactions are most typically seen in children who develop eczema as a symptom of food allergy and in people with a rare allergy to red meat caused by the bite of a lone star tick.
Another type of delayed food allergy reaction stems from food protein-induced enterocolitis syndrome (FPIES), a severe gastrointestinal reaction that generally occurs two to six hours after consuming milk, soy, certain grains and some other solid foods. It mostly occurs in young infants who are being exposed to these foods for the first time or who are being weaned. FPIES often involves repetitive vomiting and can lead to dehydration. In some instances, babies will develop bloody diarrhea. Because the symptoms resemble those of a viral illness or bacterial infection, diagnosis of FPIES may be delayed. FPIES is a medical emergency that should be treated with IV rehydration.
Not everyone who experiences symptoms after eating certain foods has a food allergy or needs to avoid that food entirely; for instance, some people experience an itchy mouth and throat after eating a raw or uncooked fruit or vegetable. This may indicate oral allergy syndrome – a reaction to pollen, not to the food itself. The immune system recognises the pollen and similar proteins in the food and directs an allergic response to it. The allergen is destroyed by heating the food, which can then be consumed with no problem.