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, macadamia nuts, pistachios, pecans, and cashews.
The body's immune system normally fights infection. But, when someone is allergic to tree nuts or peanuts, the immune system overreacts to proteins in these foods. Every time the person eats (or, in some cases, handles) a peanut or tree nut, the body thinks the proteins are harmful invaders. The immune system responds by kicking into high gear to fend off the "invader." This causes an allergic reaction, in which chemicals like histamine are released in the body.
The release of these chemicals can cause someone to have some or all of the following problems:
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.
Nut and peanut allergies can cause a severe reaction called anaphylaxis. Anaphylaxis may begin with some of the same symptoms as a less severe reaction, but then quickly worsen, leading someone to have trouble breathing, feel lightheaded, or to pass out. If it is not treated quickly, anaphylaxis can be life threatening.
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, since the protein has to be ingested (swallowed) to cause a reaction. 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 very rare 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. The person inhales and then swallows the protein, and this can lead to a reaction when the protein gets digested.
Although some people outgrow certain food allergies over time (like milk, egg, soy, and wheat allergies), peanut and tree nut allergies are lifelong in many people.
If allergy skin testing shows that someone has a peanut or tree nut allergy, a doctor will provide guidelines on what to do.
The best way to prevent a reaction in someone with 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 foods contain peanuts or tree nuts. Check the ingredients list first.
After checking the ingredients list, look on the label for phrases like these:
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 small 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:
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:
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 two types of easy-to-carry containers, one about the size of a large marker and the other about the size of a small cellphone. 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 restaurants are increasingly aware of the risks they 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. As your friends, they probably hope you'll be as considerate when it comes to taking care of them!
Reviewed by: Magee L. DeFelice, MD, and Alana Kekevian, DO
Date reviewed: September 2014
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