About Peanut and Tree Nut Allergies

First grade has been a difficult parenting year for Anne. Her 6-year-old son, Justin, began eating lunch in the cafeteria with hundreds of other students armed with their peanut butter sandwiches, peanut butter crackers, and all those hidden peanuts in their processed foods.

For Justin, who has an extremely severe allergy to peanuts, it means sitting at a peanut-free table. But Justin isn't alone: The U.S. Food and Drug Administration (FDA) estimates that 6% of children younger than 3 years old have some kind of food allergy, putting them at risk of an allergic reaction at home or, even more dangerously, away from home.

Peanuts are among the most common allergy-causing foods, and they often find their way into things you wouldn't imagine. Take chili, for example: It may be thickened with ground peanuts.

Peanuts are actually not a true nut, but a legume (in the same family as peas and lentils). But the proteins in peanuts are similar in structure to those in tree nuts. For this reason, people who are allergic to peanuts also can be allergic to tree nuts, such as almonds, Brazil nuts, walnuts, hazelnuts, macadamias, pistachios, pecans, and cashews.

The Allergic Reaction

An allergic reaction happens when someone's immune system mistakenly believes that something harmless, such as a tree nut or peanut, is actually harmful. The immune system responds by creating specific antibodies to proteins in that food. These antibodies — called immunoglobulin E (IgE) — are designed to fight off the "invading" proteins.

IgE antibodies trigger the release of certain chemicals into the body. One of these is histamine. The release of histamine can affect a person's respiratory system, gastrointestinal tract, skin, and cardiovascular system, causing allergy symptoms like wheezing, stomachache, vomiting, itchy hives, and swelling.

Reactions to foods, like peanuts and tree nuts, can be different. It all depends on the person — and sometimes the same person can react differently at different times. Some reactions can be very mild and involve only one system of the body, like hives on the skin. Other reactions can be more severe and involve more than one part of the body.

Most reactions last less than a day and affect any of these four body systems:

1. Skin. Skin reactions are the most common type of food allergy reactions. They can take the form of itchy, red, bumpy rashes (hives), eczema, or redness and swelling around the mouth or face.
2. Gastrointestinal system. Symptoms can take the form of belly cramps, nausea, vomiting, or diarrhea.
3. Respiratory system. Symptoms can range from a runny or stuffy nose, itchy, watery eyes, and sneezing to the triggering of asthma with coughing and wheezing.
4. Cardiovascular system. A person may feel lightheaded or faint and lose consciousness.

In really bad cases, an allergy can cause anaphylaxis, a sudden, potentially life-threatening reaction that, besides the symptoms mentioned above, can make airways swell and blood pressure drop. As a result, a person may have trouble breathing and could lose consciousness

Peanut reactions can be very severe, even if someone isn't exposed to much peanut protein. Experts think this might be because the immune system recognizes peanut proteins more easily than other food proteins.

Although a small amount of peanut protein can set off a severe reaction, it is rare to have an allergic reaction just from breathing in small particles of nuts or peanuts. Most foods with peanuts in them don't allow enough of the protein to escape into the air to cause a reaction. And just the smell of foods containing peanuts won't produce a reaction because the scent does not contain the protein.

In the few cases when people do react to airborne particles, it's usually in an enclosed area (like a restaurant) where lots of peanuts are being cracked from their shells. Although some people outgrow certain food allergies over time (like milk, egg, soy, and wheat allergies), peanut and tree nut allergies are lifelong in most people.

Living With Peanut or Tree Nut Allergy

If allergy testing shows that your child has a peanut or tree nut allergy, a doctor will provide guidelines on what to do.

The only real way to treat a nut allergy is to avoid peanuts and tree nuts. Avoiding nuts means more than just not eating them. It also means not eating any foods that might contain tree nuts or peanuts as ingredients.

The best way to be sure a food is nut free is to read the label. Manufacturers of foods sold in the United States must state on their labels whether the foods contain peanuts or tree nuts. Check the ingredients list first.

After checking the ingredients list, look on the label for phrases like these:

• "may contain nuts"
• "produced on shared equipment with nuts or peanuts"
• "produced in a facility that also processes nuts"

People who are allergic to nuts also have to avoid foods with these statements on the label. Although these foods might not use nut ingredients, the warnings are there to let people know they might contain traces of nuts. That can happen through "cross-contamination," when nuts get into a food product because it is made or served in a place that uses nuts in other foods.

Some of the highest-risk foods for people with peanut or tree nut allergy include:

• Cookies and baked goods. Even if baked goods don't contain nut ingredients, they might have come in contact with peanut or tree nuts through cross-contamination. Unless you know exactly what went into a food and where it was made, it's safest to avoid store-bought or bakery cookies and other baked goods.
  
  
• Candy. Candies made by small bakeries or manufacturers (or homemade candies) may contain nuts as a hidden ingredient. The safest plan is to eat only candies made by major manufacturers whose labels show they are safe.
  
  
• Ice cream. Unfortunately, cross-contamination is common in ice cream parlors because of shared scoops. It's also a possibility in soft-serve ice cream, custard, or yogurt places because the same dispensing machine is often used for lots of different flavors. Instead, do as you would for candy: Buy tubs of ice cream at the supermarket and be sure they're made by a large manufacturer and the labels indicate they're safe.
  
  
• Asian, African, and other cuisine. African and Asian (especially Thai and Indian) foods often contain peanuts or tree nuts. Mexican and Mediterranean foods may also use nuts, so the risk of cross-contamination is high with these foods.
  
  
• Sauces. Many cooks use peanuts or peanut butter to thicken chili and other sauces.

Always proceed with caution. Even if your child has eaten a food in the past, manufacturers sometimes change their processes — for example, switching suppliers to a company that uses shared equipment. And two foods that seem the same might have differences in their manufacturing.

To help reduce contact with nut allergens and the possibility of severe reactions (anaphylaxis) in someone with a peanut or tree nut allergy:

• Consider making your entire home nut-free.
  
• If you do allow nuts in your home, watch for cross-contamination that can happen with utensils and cookware. For example, make sure the knife you use to make peanut butter sandwiches is not used in preparing food for a child with a nut allergy, and that nut breads are not toasted in the same toaster as other breads.
• Don't serve cooked foods you didn't make yourself, or anything with an unknown list of ingredients.
• Tell everyone who handles the food your child eats, from waiters and waitresses to the cafeteria staff at school, about the allergy. If the manager or owner of a restaurant is uncomfortable about your request for peanut- or nut-free food preparation, don't eat there.
• Consider making your child's school lunches, as well as snacks and treats to take to parties, play dates, sleepovers, school functions, and other outings.
• Talk to the daycare supervisor or school principal before your child attends. Work together to create a food allergy emergency action plan.
• Keep epinephrine accessible at all times — not in the glove compartment of your car, but with you, because seconds count during an anaphylaxis episode.

With a little preparation, and prevention, you can ensure that your child's allergy doesn't get in the way of a happy, healthy, everyday life.

Reviewed by: Magee L. DeFelice, MD, and Sheelagh M. Stewart, RN, MPH
Date reviewed: October 2011