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 aren't actually a true nut; they're 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 can also be allergic to tree nuts, such as almonds, Brazil nuts, walnuts, hazelnuts, macadamias, pistachios, pecans, and cashews.
What Happens With a Nut or Peanut Allergy?
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 (pronounced: hiss-tuh-meen). 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:
- 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.
- Gastrointestinal system. Symptoms can take the form of belly cramps, nausea, vomiting, or diarrhea.
- 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.
- Cardiovascular system. A person may feel lightheaded or faint and lose consciousness.
In really bad cases, tree nut and peanut allergies can cause a condition called anaphylaxis (pronounced: ah-nuh-fuh-lak-sus). Anaphylaxis is a sudden, potentially life-threatening reaction that, in addition to the symptoms mentioned above, can make someone's airways swell and blood pressure drop. As a result, the person may have trouble breathing and could lose consciousness.
Peanut reactions can be very severe, even if a person 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 that people get 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 or bar) 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 someone 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 have to state on their labels whether 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 the food may contain traces of nuts. That can happen through something called "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, it is possible that they came into 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 you are used to eating a particular food. Even if you've 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 also have differences in their manufacturing.
Here are some other precautions you can take:
- Be on the watch for cross-contamination that can happen on kitchen surfaces and utensils — everything from knives and cutting boards to the toaster. Make sure the knife another family member used to make peanut butter sandwiches is not used to butter your bread and that nut breads are not toasted in the same toaster you use. You may decide to make your home entirely nut-free.
- Avoid cooked foods you didn't make yourself — anything with an unknown list of ingredients.
- Tell everyone who handles the food you eat, from relatives to restaurant waitstaff, that you have a nut 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.
- Make school lunches and snacks at home where you can control the preparation.
- Be sure your school knows about your allergy and has an action plan in place for you.
- Keep rescue medications (such as epinephrine) accessible at all times — not in your locker, but in a pocket, purse, or bookbag that's with you. Seconds count during an episode of anaphylaxis.
Managing Serious Reactions
If someone is diagnosed with a life-threatening peanut or tree nut allergy (or any kind of life-threatening food allergy), the doctor will want that person to carry an epinephrine (pronounced: eh-puh-neh-frin) auto-injector in case of an emergency. Epinephrine comes in an easy-to-carry container about the size of a large marker. It's easy to use — if you need to carry epinephrine, your doctor will show you how to use it.
Keeping epinephrine on hand at all times should be just part of your action plan for living with a peanut or tree nut allergy. It's also a good idea to carry an over-the-counter (OTC) antihistamine as this can help treat mild allergy symptoms. Use antihistamines in addition to — not as a replacement for — the epinephrine shot in life-threatening reactions, and always use the epinephrine shot as the first treatment. Get emergency care after epinephrine is used, because a second reaction can happen up to 4 hours or even longer after the first reaction.
Living with allergies can seem hard at times. But as more and more people are diagnosed with food allergies, businesses and individuals are increasingly aware of the risks people with food allergies face.
If friends you're visiting or eating lunch with don't know about your allergy, tell them in plenty of time to make some simple preparations (such as not sharing your drink after eating that peanut butter sandwich!). Chances are, they'll understand. After all, as your friends they'd no doubt hope for the same from you!
Reviewed by: Magee Defelice, MD, and Sheelagh M. Stewart, RN, MPH
Date reviewed: October 2011
Originally reviewed by: Hemant P. Sharma, MD
Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.
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