By: Daniel DiGiacomo, MD, MPH, FAAP & Anthony Porto, MD, MPH, MBA, FAAP
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food allergy happens when the body reacts against harmless proteins found in foods. These proteins are called allergens. Food allergy reactions can vary from mild to severe and life threatening.
Food allergies are most common in babies and children, but they can occur at any age. They also occur more often in children who have other allergies or who have family members with allergies.
Most common food allergies
Any food could cause a food allergy, but most food allergies are caused by these foods or food groups:
Cow's milk
Eggs
Peanuts
Soy
Wheat
Nuts from trees (such as walnuts, pistachios, pecans, cashews)
Fish (such as tuna, salmon, cod) & shellfish (such as shrimp, lobster)
Sesame
Peanuts, nuts, milk and sesame are the most common causes of severe reactions. Allergies also occur to other foods such as meats, fruits, vegetables and grains. Sometimes, a food allergy may be to one specific food in a category. For example, a child allergic to peanuts (which is a type of bean), may not be allergic to other beans like soybeans or green beans.
Signs & symptoms of food allergies in children & teens
Symptoms can develop after eating, inhaling or coming in contact with food allergens. Each child's
food allergy symptoms are different. When the body's immune system overreacts to certain foods, the following symptoms may occur:
Skin problems: hives, itchy skin rashes, swelling
Breathing problems: sneezing, wheezing, throat tightness, coughing, nasal congestion and runny nose
Stomach & gastrointestinal tract symptoms: nausea, vomiting, diarrhea, abdominal pain and cramps, trouble swallowing
Circulation symptoms: skin looks more pale than usual, light-headedness, chest pain, feeling faint or confused, loss of consciousness
Food allergy symptoms in babies
Babies can have different symptoms of an allergic reaction, as well. These may include eye rubbing, repetitively sticking tongue out, excessive crying, arching of the back and decreased muscle tone.
How are food allergies treated?
Emergency treatment for a food allergy reaction
Epinephrine is the main medicine to treat a severe allergic reaction called
anaphylaxis. The medicine is available in auto-injectors and nasal spray for emergency use. Anyone who has ever had an allergic reaction to food should always have at least two doses of epinephrine auto-injector or nasal spray readily available. Epinephrine can be prescribed by your pediatrician or allergist/immunologist.
Ask your child's doctor what to do if the symptoms do not improve very quickly after a single dose.
For anyone experiencing
anaphylaxis, epinephrine should be given right away followed by a call to 911 for further treatment and transfer to a hospital. During a reaction, an oral antihistamine such as diphenhydramine may also be given, but not in place of epinephrine. Also helpful in case of an emergency is medical identification jewelry that includes information about your child's allergy. This should be worn at all times.
Preventive treatment for food allergy reactions
Avoiding foods that contain a known allergen helps avoid an allergic reaction. In addition, there are treatments that can help prevent a child from having an allergic reaction to food. These include:
A medication called omalizumab can stop an allergic reaction to food from becoming severe if a child is exposed to it.
A treatment called oral immunotherapy can help desensitize your child's immune system. It involves introducing a very small amount of food and slowly increasing the amount.
These treatments, which can be prescribed by an allergist/immunologist, do not cure the food allergy. Your child will still need to avoid food if they are allergic to it.
Can introducing allergens early help prevent food allergies?
Starting around 6 months, parents can help lower the risk of food allergies by offering common allergens like peanuts, eggs, dairy and sesame. Delaying the introduction of these foods may actually raise the risk. Begin with small amounts, one food at a time, and watch for reactions. If your baby has eczema or a family history of allergies, check with your pediatrician first. Safe, early exposure can make a big difference.
(See "When to Introduce Egg, Peanut Butter & Other Common Food Allergens to a Baby.")How are food allergies diagnosed?
If your child has a reaction after eating, their doctor will try to figure out which food caused it. This can be tricky if the meal had lots of ingredients. And if your child has chronic symptoms, such as skin rashes or stomachaches, many foods in the diet must be looked at as possible causes.
Medical history & physical exam
The doctor will ask detailed questions about the suspected food, how long after eating it symptoms started, how severe the symptoms were, how long they lasted and what treatment was needed. They'll also perform a physical exam. Based on this history and physical exam, the doctor may order a skin or blood test.
Allergy testing
Allergy tests, including a skin prick "scratch" test or blood tests can help narrow down possible causes. However, skin tests and blood tests are not always reliable. It is possible to have a positive test but no symptoms after eating the food—or test negative and still have an allergy.
The doctor may refer you to an allergist, who specializes in diagnosing and managing food allergies.
Fast-acting v. slow-acting food allergies
Fast-Acting Allergies (IgE-Mediated)
This is the most common kind of food allergy. It happens when the body makes a special protein antibody called immunoglobulin E (IgE) that reacts to certain foods. These reactions usually happen quickly—within minutes or a few hours after eating.
Slow-Acting Allergies (Non-IgE-Mediated)
These allergies don't use the IgE protein and take longer to show up—sometimes days later. Examples of non-IgE-mediated allergy include:
When it's not a food allergy
Food can cause many illnesses that are sometimes confused with food allergies. The following are not food allergies:
Food poisoning: Can cause diarrhea or vomiting, but is usually caused by bacteria in spoiled food or undercooked food.
Drug effects: Certain ingredients, such as caffeine in soda or candy, can make your child shaky or restless.
Skin irritation: Can often be caused by acids found in such foods as orange juice or tomato products.
Diarrhea: Can occur in small children from too much sugar, such as from fruit juices.
Food intolerance or sensitivity v. food allergy
Not all bad reactions to food are allergies. Some are called food intolerances or sensitivities because they don't involve the immune system. For example, lactose intolerance happens when someone has trouble digesting the sugar in milk, which can cause stomach pain, gas, or diarrhea. People can also react to chemicals added to foods, like dyes or preservatives. These reactions are usually sensitivities, not true allergies, which are much less common.Can children outgrow food allergies?
Yes, children often outgrow food allergies. The majority of egg, milk, wheat, and soy allergies go away by age 5 years. But some allergies are more persistent. For example, only 20% to 25% of children with peanut allergies and 10% of kids with tree nut allergies outgrow them. Your allergist can perform tests to track your child's food allergies and watch to see if they are going away.
Living with a food allergy: tips for families
Avoiding foods if your child has a known allergy
Food bought from a store. Read food labels carefully. Check them every time you buy a product because ingredients can change. Also, sometimes ingredients are not fully labeled. Words such as "natural flavors" or "spices" could include a variety of ingredients. Some food labels include precautionary statements like "may contain...." You may need to contact the manufacturer to find out the exact ingredients.
Food made at home. If the food your child is allergic to is used in your home, be careful not to mix it into your child's "safe" food. To avoid cross-contact, make sure to use clean utensils, plates, pans, and serving trays. Also do not store unsafe foods with safe foods.
Food made in restaurants. Cross-contamination or hidden ingredients in prepared foods can cause allergic reactions. Careful planning and clear communication with those preparing the food is very important if you eat at a restaurant. Speak with someone at the restaurant who truly knows the ingredients and how the food is prepared.
Creating and sharing allergy & anaphylaxis action plans
- When your child is away from you, including at a family or friend's house, at school, a child care center or camp, have a written plan. The plan should outline what needs to happen to avoid problem foods, recognize and treat a reaction and get medical care.
See "Create an Allergy and Anaphylaxis Emergency Plan."
More information
About Dr. DiGiacomo
 Daniel DiGiacomo, MD, MPH, FAAP, is a Pediatric Allergist/Immunologist at K. Hovnanian Children's Hospital at Jersey Shore University Medical Center. He completed his pediatrics residency at Children's National Medical Center and fellowship training at Massachusetts General Hospital in Boston. Dr. DiGiacomo, a member of the American Academy of Pediatrics (AAP) Sections on Allergy and Immunology and Epidemiology, Public Health and Evidence, has a clinical interest in infant food allergy. He enjoys spending time at the beach with his family during his time off, and is an avid New York sports fan.
About Dr. Porto
 Anthony Porto, MD, MPH, FAAP, is a board-certified pediatrician and board-certified pediatric gastroenterologist. He is a Professor of Pediatrics and Associate Chief of Pediatric Gastroenterology at Yale University and Medical Director, Pediatrics, at Greenwich Hospital in Greenwich, CT. He is also the medical director of the Yale Pediatric Celiac Program. Dr. Porto is a member of the AAP Section on Gastroenterology, Hepatology and Nutrition and the North American Society of Pediatric Gastroenterology, Hepatology and Nutrition's Public Education Committee. He is the co-author of The Pediatrician's Guide to Feeding Babies and Toddlers. Follow him on Instagram @Pediatriciansguide.
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