The Doctor Is In is an occasional series where JHU Press authors discuss the latest developments and news in health and medicine. Guest post by Scott H. Sicherer, M.D. Food allergy appears to be on the rise in children: studies show that up to 8% of children are estimated to have a food allergy, and the rate of peanut allergy among children has tripled in the last decade. What should you do if you suspect your child has a food allergy? And how you can work with your doctor to obtain a proper diagnosis? When to Suspect a Food Allergy A food allergy occurs when the body’s immune system, which is designed to fight infection, mistakenly attacks harmless proteins in foods. This “attack” can cause sudden symptoms just after a food is eaten or, more rarely, persistent symptoms when a causal food is a staple of the diet. Some common mild symptoms include hives, swelling (often of the lips or around the eyes), rash, mouth/throat itch, stomach pain, nausea, and vomiting. More severe symptoms include breathing problems, throat tightness, tongue swelling, wheezing, coughing, and trouble swallowing. Problems with blood circulation, leading to paleness, confusion, and faintness, could also occur. More severely, a food allergy can trigger anaphylaxis, an extreme allergic reaction that progresses rapidly and can be fatal. Food allergies can also cause chronic symptoms. Infants may have vomiting, diarrhea, poor growth, chronic rashes, or mucous and blood in their stools. A child may experience pain when eating or not be gaining weight. While food can be a trigger, these problems can be caused by many other illnesses. Foods can also trigger many symptoms that are not caused by an allergy, which can lead to a delayed diagnosis or misdiagnosis. For example, lactose intolerance—difficulty in digesting the sugar in milk—leads to gas and diarrhea. Food poisoning can result in vomiting and diarrhea. To add further confusion, typical allergic symptoms could be triggered by viruses or allergens that are not foods, such as medication or exposure to a cat. In addition, the chemicals in foods can contribute to allergy-like symptoms: caffeine, for example, can cause heart palpitations, and fermented foods may cause headaches. Discussing Possible Food Allergies with Your Doctor If your child has experienced allergic symptoms, you should talk to your pediatrician about your concerns or see a Board-Certified Allergist. Come prepared to answer the following questions: What are your child's symptoms? What foods or meals are associated with the symptoms? Have you noticed a pattern? Do symptoms always occur when your child eats certain ingredients? How much of the food triggers symptoms? More than 90% of allergies are attributed to milk, eggs, peanuts, wheat, soy, tree nuts (e.g., walnuts, cashews, etc.), and fish and shellfish, although any food could trigger an allergy. Your pediatrician will be especially suspicious of foods that are not eaten routinely but, when eaten, are associated with symptoms. Allergy Tests Unfortunately, there are no simple laboratory tests currently available that accurately diagnose food allergy. One blood test detects a protein called “IgE,” which is at the root cause of most food-based allergic reactions. The problem is that many people without a food allergy make IgE proteins, so this test is helpful but not definitive; in some cases, it may be negative, despite the presence of an allergy. Ultimately, the most important factor in identifying allergies is a child’s medical history. Your doctor must consider your child’s individual circumstances in order to develop a best guess about what foods might be acting as possible allergens. They must also use this history to select and interpret tests accordingly. There is no need for your doctor to test foods that are not likely to be a concern. For example, about one in 12 people who are able to eat peanuts will test positive for peanut allergies. If your peanut-eating child tests positive for peanut allergy, then the test is meaningless. However, if you have a child who breaks out in hives after eating peanuts, a positive test could confirm that they are allergic. An allergist can also perform skin tests by scratching a small amount of a diluted food extract onto the skin. If a small, itchy bump develops on the scratch, the child is allergic to that particular extract. These skin and blood tests are similar with regard to their ability to detect the IgE, although sometimes one or the other might be a bit better for a specific food. The stronger the positive result, the more likely there is truly an allergy. However, the test is not a good predictor of the severity of an allergy. The most definitive food allergy test is a gradual, doctor-supervised feeding of the suspected allergen, which is typically undertaken by an allergist. If the allergist observes an allergic reaction, the feeding is stopped and the symptoms are treated. If the child tolerates the food without exhibiting any symptoms, there is no allergy, even if the blood or skin test was positive. Managing a Food Allergy A true food allergy requires that your child avoid the food in order to avoid experiencing symptoms. Additionally, you will need to learn about allergen avoidance. This means understanding how to read food labels, avoiding cross contact during meal preparation, discussing your child’s allergy at restaurants, teaching other caretakers about food allergies, and managing your child’s allergy at school or camp. There are excellent resources for learning about these steps, including Food Allergy Research & Education, the Consortium of Food Allergy Research, and the American Academy of Allergy, Asthma & Immunology, a professional allergy society. If your doctor determines that your child’s allergy is particularly severe, he will prescribe an autoinjector for epinephrine. This medication reverses serious symptoms, giving you time to seek emergency care. Ask your doctor to explain when and how the medication is to be used and to provide you with written materials. In summary, if you suspect that your child has a food allergy, work with your doctor to secure a diagnosis and create a treatment plan. Many childhood food allergies will resolve, so be sure to get yearly re-evaluations to discuss management and determine if the allergies have gone away. Scott Sicherer, M.D., is a professor of pediatrics and chief of the Division of Pediatric Allergy and Immunology at Mount Sinai School of Medicine, New York. He is also a researcher in the Jaffe Food Allergy Institute at Mount Sinai. He is the author of Food Allergies: A Complete Guide for Eating When Your Life Depends on It and Understanding and Managing Your Child’s Food Allergies, both published by Johns Hopkins.