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.
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 an allergic 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 minor 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), 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:
Once a food allergy is diagnosed, the most effective treatment is to avoid the food. The foods most associated with food allergy in children are:
Children may outgrow their allergic reactions to milk and eggs. Peanut and tree nut allergies are likely to persist.
The most common food allergens in adults are:
People allergic to a specific food may also potentially react to related foods. A person allergic to one tree nut may be cross-reactive to others. Those allergic to shrimp may react to crab and lobster. Someone allergic to peanuts – which actually are legumes (beans), not nuts – may have problems with tree nuts, such as pecans, walnuts, almonds, and cashews; in very rare circumstances, they may have problems with other legumes (including soy).
Learning about patterns of cross-reactivity and what must be avoided is one of the reasons why people with food allergies should receive care from a board-certified allergist. Allergy testing to many items in the same “family” may not be specific enough – many times, these tests are positive, given how similar two food items in a “family” may look to the test. If you have tolerated it well in the past, a food that is theoretically cross-reactive may not have to be avoided at all. This requires an allergy specialist to help define when a food is safe to eat.
Negative tests may be beneficial in ruling out an allergy. In the case of positive tests on foods that you have never eaten but that are related to items to which you’ve had an allergic reaction, an oral food challenge is the best way to determine whether the food poses a danger.
Because fatal and near-fatal food allergy reactions can occur at school or other places outside the home, parents of a child with food allergies need to make sure that their child’s school has a written emergency action plan. The plan should provide instructions on preventing, recognizing, and managing food allergies and should be available in the school and during activities such as sporting events and field trips. If your child has been prescribed an epinephrine auto-injector, be sure that you and those responsible for supervising your child understand how to use it.