Reviewed by Hansa D. Bhargava, MD, FAAP on June 27, 2011
Sources: © 2011 WebMD
Peanuts
Peanuts cause more life-threatening allergic reactions than any other food. They’re a legume, like soybeans, rather than a true nut. Â But among people with a peanut allergy, 25%-50% will also react to tree nuts, such as walnuts. Foods and ingredients to avoid include beer nuts, goobers, arachic oil, and some hydrolyzed vegetable proteins. Baked goods, sauces, even chili can contain hidden peanut proteins.
Milk and Dairy Foods
A milk allergy is the most common food allergy in children, but 80% outgrow it. Infants may need hypoallergenic or soy formula, and sometimes breastfeeding mothers need to avoid drinking milk. Milk proteins, including casein, are ubiquitous in processed foods, even found in canned tuna. If you’re allergic to cow’s milk, goat’s milk may not be safe, either. Lactose intolerance is not an allergy, but a digestive problem.
Eggs
Eggs are the second most common cause of food allergy in children, although they usually outgrow this allergy, as well. Read the labels carefully for noodles, mayonnaise, and baked goods. Eggs can also be found in some unlikely products: the foam topping in drinks or the egg wash on pretzels. Eggs are used to produce the influenza vaccine, so check with a doctor before getting the flu vaccine.
Shellfish
An allergy to shellfish most often develops in adulthood, and it is a lifelong allergy. Shrimp, crab, crawfish, and lobster — crustaceans — produce the most severe allergic reactions. Mollusks can trigger reactions, too: clams, mussels, scallops, escargot, octopuses, and squid. People allergic to shellfish should avoid steam tables or stovetops where shellfish is cooked because the vapors can trigger a reaction.
Tree Nuts
Walnuts, almonds, pecans, hazelnuts, cashews, pistachios, Brazil nuts, and pine nuts may all be off limits if you have a tree nut allergy. These must be clearly labeled in packaged foods, but nuts are more difficult to avoid in restaurants and bakeries. Nutmeg, water chestnuts, sunflower seeds, and sesame are not nuts and can be eaten safely. Be aware that tree nut oils, such as shea oil, may be used in skin lotions.
Finned Fish
The protein in finned fish can cause severe allergies, most commonly from eating salmon, tuna, or halibut. Â If you’re allergic to one type, you may react to others, too. Â Many ethnic restaurants flavor dishes with fish sauces. Â So tread carefully in Thai and Chinese restaurants, and beware of Caesar dressing and Worcestershire sauce, made from anchovies. Some people can safely eat canned tuna and salmon, but not fresh fish.
Soy
If you’re allergic to soy, you need to read the fine print very carefully on food labels. Soy protein is widely used in breads, cookies, canned soups, processed meats, and snack foods. Foods  to avoid include edamame, (young green soybeans), tofu, soy milk, miso, and soy sauce. Most people with soy allergy can still eat soy oil and soy lecithin. Soy allergy is more common among babies and children.
Wheat
Wheat allergy is an allergic reaction to one of four proteins in wheat. You do not necessarily react to the gluten. People allergic to wheat can usually eat other grains, including barley, oats, rye, corn, and rice. Wheat allergy is more common among children and is often outgrown. Bulgur, couscous, and farina contain wheat protein, and many products, including beer, salad dressing, and processed meats, may contain wheat.
Contrast: Gluten Intolerance
People with celiac disease have an autoimmune disorder that is triggered by gluten, a protein in wheat, rye, and barley. Eating gluten actually damages the small intestine. Symptoms include diarrhea, bloating, weight loss, chronic fatigue, and weakness — but not the skin rashes, swelling, or wheezing seen with a food allergy. Some people may have gluten intolerance that is a digestive problem and not immune-related. Celiac disease can be diagnosed with a blood test.
How a Food Allergy Begins
With the first exposure to a trigger food, your body treats it as something harmful and creates immunoglobulin E antibodies in your blood stream. You won’t notice symptoms at the first exposure, but your body is primed to release histamine the next time. Although some food allergies are more common among young children, food allergies can develop at any time in life.
Symptoms usually occur within a few minutes to two hours after eating the food. Reactions range from mild to severe and can include:
- Hives or other skin rash
- Tingling or itching in the mouth
- Swelling of face, tongue, or lips
- Coughing or wheezing
- Vomiting, diarrhea, or abdominal cramps
- Swelling of throat and vocal chords
- Difficulty breathing
