Peanuts

When you're allergic to a food, your body reacts to proteins in that food. It can cause rashes, swelling, trouble breathing. Peanuts can be in a lot -- from baked goods to sauces. Read food labels. Packaged foods must say if they have peanuts. Ask how food is prepared and let servers know you’re allergic. If you’re allergic to peanuts, tree nuts, like walnuts, may bother you too.

Milk and Dairy Foods

Milk is one of the most common food allergy trigger for kids. The good news -- most outgrow it. In the meantime, infants may need hypoallergenic or soy formula.If you’re breastfeeding, you may need to avoid drinking milk too. Look at the label on packaged foods. Even things like tuna can have milk protein in it. Sometimes milk is listed as the ingredient casein.

Eggs

These are another common food allergy trigger for kids. While many outgrow this allergy, watch out for eggs in noodles, mayonnaise, and baked goods. They can also be in some unlikely places like  the foam topping on drinks or the egg wash on pretzels. Eggs are also used to make the flu vaccine, so check with your doctor before getting it.

Shellfish

Surprise! You can get a sudden seafood allergy as an adult. If you do, sorry seafood lovers, it’ll stick with you for life. Shrimp, crab, crawfish, and lobster -- these guys can cause serious reactions. Clams, mussels, scallops, escargot, octopuses, and squid can cause reactions, too. If you’re allergic, avoid all shellfish.

Tree Nuts

It can seem like nuts are everywhere. They can even be in lotions made from tree nut oils, like shea oil. Nuts must be listed on packaged foods, but they're harder to avoid in restaurants and bakeries. If you’re allergic, watch out for walnuts, almonds, pecans, hazelnuts, cashews, pistachios, Brazil nuts, and pine nuts. Nutmeg, water chestnuts, sunflower seeds, and sesame seeds aren't nuts and should be OK.

Fish

Fresh salmon, tuna, or halibut can cause severe allergies. If you’re allergic to one type of fish, you may react to others, too. Be careful if you love Thai and Chinese food. Many ethnic restaurants flavor dishes with fish sauce. Also beware of Caesar dressing and Worcestershire sauce. They have  anchovies in them.

Soy

Breads, cookies, canned soups, processed meats, and snack foods all can have soy in them. If you’re allergic, read food labels carefully so you can steer clear. Other foods to avoid include edamame, tofu, soy milk, miso, and soy sauce. Babies and children are more likely to have a soy allergy than adults.

Wheat

From bread to beer, salad dressing to deli meats, wheat can hide in a lot of foods. Why? Wheat proteins help some processed food stick together and give it texture. If you’re allergic to wheat, other grains, like barley, oats, rye, corn, and rice are usually safe. But you may want to avoid bulgur, couscous, and farina. It's possible to have a wheat allergy but be OK to eat gluten.

Gluten Sensitivity? Intolerance?

If you’re gluten-sensitive, that’s different from an allergy. Gluten is usually found in wheat, rye, and barley. It can trigger:

A gluten allergy -- Your immune system thinks food with gluten, like wheat, are dangerous.

Gluten Intolerance or Celiac disease -- Gluten can cause permanent damage to your intestines.

Gluten sensitivity -- Your stomach and intestines are upset by gluten. It doesn’t cause permanent damage but you may want to avoid it.

How a Food Allergy Starts

You eat or drink a trigger food and your immune system thinks that it is something bad. You won’t notice any allergy symptoms like a rash or itching this first time, but your body will be on the lookout for that food again. The next time you eat it, since your body thinks the food is bad, it’ll release histamine. Histamine is what causes a lot of allergy symptoms like rashes, itching, and swelling.

Food Allergy Symptoms

If you eat something you’re allergic to, you’ll usually get allergy symptoms pretty quickly. It could take just a few minutes to two hours. You could have:

• Hives or other skin rash
• Tingling or itching in your mouth
• Swelling of face, tongue, or lips
• Coughing or wheezing
• Vomiting, diarrhea, or abdominal cramps
• Swelling of throat and vocal chords
• Difficulty breathing

Anaphylaxis: Severe Reaction

Symptoms can sometimes be so bad that they can be life-threatening. This is called anaphylaxis. When this happens it can tighten someone’s airways and throat so much that they can’t breathe. Their blood pressure can drop fast. If you have food allergies, your doctor may prescribe epinephrine (EpiPen) to always carry with you. Use the injection at the first sign of a reaction. Then go to an emergency room.

Myth: Food Allergies Are Predictable

One bite of seafood went down OK last time. Does that mean one bite is always safe? Maybe, maybe not. In general, how much of an allergic reaction you’ll have depends on how bad your allergy is and how much of the trigger food you eat. But reactions can be unpredictable. While you may have hives one time, you could  have vomiting or breathing problems next time.

Food Intolerance, Not an Allergy

If you have trouble digesting a food -- like milk or gluten -- that isn’t the same as a food allergy. An allergy is caused by an immune system reaction. Food intolerance, such as lactose intolerance, can cause bloating, cramps, and diarrhea. But it doesn’t cause an immune system reaction. Lactose intolerance happens when your body can’t break down lactose, the sugar in milk and dairy products.

Food Additives, Not Always an Allergy

You can have a reaction to food additives without being allergic. Monosodium glutamate (MSG) can cause flushing, warmth, headache, and chest discomfort. Sulfites, which are found in some dried fruits, wine, and other foods, can cause breathing problems for people with asthma. The FDA requires sulfites to be listed on labels. It also banned their use on fresh fruits and vegetables.

Oral Allergy Syndrome

An allergy to fresh fruits and vegetables is called oral allergy syndrome. People who have hay fever, especially hay fever triggered by birch or ragweed pollen, are most likely to get it. Uncooked apples, cherries, kiwis, celery, tomatoes, and green peppers may cause tingling, itching or swelling of the lips, tongue or throat. They can also cause watery or itchy eyes, a runny nose, and sneezing.

Exercise-Induced Food Allergy

This only happens  in some people when they eat a trigger food right before exercising. Their body temperature rises and the food can trigger an allergic reaction. It can cause itching, hives, lightheadedness, or  anaphylaxis. The foods most likely to trigger this type of allergy are shellfish, alcohol, tomatoes, cheese, and celery. Avoid trigger foods for a couple of hours before you exercise.

Elimination Diet

If you’re not sure what caused an allergic reaction, you may want to write down what you eat and how you feel. It may clue you in to possible triggers. You could also talk to a doctor about going on an elimination diet. On this plan, you stop eating one suspicious food at a time, eliminating it from your diet. This may help you figure out which food is causing your allergy.

Allergy Testing

You may be able to find out what you’re allergic to by getting tests.

Skin prick test -- An allergist puts a drop of liquid on your skin, then pricks the skin to allow it to soak in. No reaction means you’re not allergic. This is the most common allergy test.

Blood test – By taking a sample of your blood, they can see if it reacts to certain triggers.

Supervised food challenge – While a doctor watches, you eat foods to see if you react.

Outgrowing Allergies

Children are likely to outgrow allergies to milk, egg, wheat, and soy. However, kids with peanut, tree nut, fish, and shellfish allergies usually have them for life. If you want to see if your child has outgrown her allergy, your doctor can do a blood test. Do not try to feed your child a food on your own to check. Even a small amount of a food can cause a life-threatening reaction.

Living With Food Allergies

With no cure for food allergies, you need to avoid your trigger foods. Have a food allergy action plan for yourself or your allergic child. Use an epinephrine injection and then call 911 at signs of anaphylaxis (wheezing, trouble breathing, dizziness).  You may want to wear a medical ID bracelet indicating the allergy. Knowing more about your allergy can make living with it easier.

Related Reading

• Symptoms of Food Allergies
• Birth Order Link to Food Allergies
• Have Schools Gone Too Far?
• Food Allergy vs. Food Intolerance
• Peanut Allergies on the Rise
• The Truth About Food Allergy Tests
• Food Allergy Community
• Video: Outgrow a Peanut Allergy?