We all eat to survive, and most of us enjoy eating. However, people with food allergies live with the day-to-day anxiety that they may accidentally eat a food that can lead to a dangerous reaction. Approximately 30,000 Americans are treated each year for severe food allergies. About 150–200 Americans die each year because of food allergic reactions.

Food allergies, ranging from irritating to life-threatening, affect 2 percent of adults and 4–8 percent of children in the United States. According to the Centers for Disease Control, the number of young children with food allergies has increased over the past decade. Food allergies generally develop early but can occur at any age. Children usually outgrow egg, milk and soy allergies but not peanut allergies; adults who develop allergies usually have them for life. The severity of reactions can change throughout a person’s life. Allergies to tree nuts and shellfish also tend to be lifelong.

Normally, the immune system defends against potentially harmful substances such as bacteria, viruses and toxins. In some people, a food allergy develops when the immune system triggers an abnormal response to a food. Tree nuts and peanuts are the leading causes of anaphylaxis, serious deadly allergic reactions.

The FDA defines the top food allergens as milk, eggs, wheat, soy, fish, shellfish, peanuts and tree nuts. In adults, most reactions are triggered by fish, shellfish, peanuts, tree nuts and eggs; and in children, eggs, milk (especially infants and young children) and peanuts. Sometimes a reaction to food is not an allergy but an intolerance; the symptoms can mimic those of a food allergy.

The first time a person is exposed to the food no symptoms occur, but the body has been primed. When the person eats the food again, an allergic response occurs within a few minutes to several hours. The digestion process and the location of the immune cells involved in the response affect the timing and location of the reaction.

Sometimes exposure to a trigger food occurs without your knowledge. A person who experiences anaphylaxis on the first known exposure to peanuts may have previously had contact with peanuts through touching, using a peanut-containing skincare product or breathing in peanut dust.

Generally, you are at greater risk of developing a food allergy if there is a family history of any allergies, including asthma or eczema. Having two parents with allergies makes you more likely to develop food allergies.

Symptoms range from mild to severe. If you are allergic to a particular food, you may experience itching in your mouth or swelling; gastrointestinal symptoms such as vomiting, diarrhea, abdominal cramps or pain; hives or eczema; tightening of the throat or difficulty breathing; or a drop in blood pressure. These may lead to life-threatening cardiovascular collapse or cardiac arrest from anaphylactic shock.

Anaphylaxis is a serious reaction that happens quickly. Symptoms may include difficulty breathing, dizziness or loss of consciousness. Without immediate treatment, such as an injection of epinephrine and expert care, anaphylaxis can be fatal. Follow-up with an allergist/immunologist is essential.

If you or someone you are with has these symptoms, particularly after eating, seek medical assistance immediately. In the United States, call 911. If planning to travel abroad, register with the U.S. embassy in your destination country. You can find contact and registration information on the U.S. Department of State website (www.usembassy.gov). The CDC’s Yellow Book 2012 also provides information on medical services abroad. Visit www.cdc.gov and click “Y” on the alphabetical index for a link to the Yellow Book. If symptoms strike while you are traveling, contact the concierge at your hotel for information about a local medical provider.

When you have food allergies, be prepared for unintentional exposure. With your physician or allergist, develop a treatment plan in case of accident, such as wearing a medic alert bracelet or necklace and carrying an auto-injector device containing epinephrine. Ask your doctor what medicines may relieve mild symptoms not part of an anaphylactic reaction. Be aware, it may be difficult to know which reactions are mild and which may lead to anaphylaxis.

There is currently no cure for food allergies, and treatments only ease the symptoms. Prevent reactions by avoiding the allergenic food. Once you and your healthcare provider identify the food to which you are sensitive, remove it from your diet. This may be easy if the food is uncommon or easily identified. Read all labels for ingredients. Many allergens, such as peanuts, eggs and milk, appear in prepared foods. You may need to severely restrict your diet and ask detailed questions when traveling or eating away from home. Cleanliness measures can remove allergens from the environment. Washing your hands with soap and water will remove peanut allergens; most household cleaners will remove allergens from surfaces.

Breastfeeding infants may help prevent allergies. Otherwise, there is no known way to prevent food allergies except to delay introducing allergy-causing foods to infants until their gastrointestinal tracts mature. The timing varies from food to food and baby to baby. Your pediatrician can guide you.

A number of websites and organizations offer information and forums for discussing food allergies. You may find it helpful to join a support group such as the Food Allergy and Anaphylaxis Network (www.foodallergy.org).