What Is a Peanut Allergy?

Peanuts are among the most common allergy-causing foods, and they often find their way into things you wouldn't expect. 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, macadamia nuts, pistachios, pecans, and cashews.

Sometimes people outgrow some food allergies over time (like milk, egg, soy, and wheat allergies), but peanut and tree nut allergies are lifelong in many people.

What Happens With a Peanut Allergy?

When someone has a peanut allergy, the body's immune system, which normally fights infections, overreacts to proteins in peanuts. If the person eats something that contains peanuts, the body thinks these proteins are harmful invaders and responds by working very hard to fight off the invader. This causes an allergic reaction.

Even a small amount of peanut protein can set off a reaction. But allergic reactions from breathing in small particles of peanuts are rare. That's because peanuts usually need to be eaten 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 cause one because the scent doesn't contain the protein.

What Are the Signs & Symptoms of a Peanut Allergy?

When someone with a peanut allergy eats or drinks something with peanuts in it, the body releases chemicals like .

This can cause symptoms such as:

• wheezing
• trouble breathing
• coughing
• sneezing
• hoarseness
• throat tightness
• stomachache
• vomiting
• diarrhea
• itchy, watery, or swollen eyes
• hives
• swelling
• a drop in blood pressure
• dizziness or fainting
• anxiety or a feeling something bad is happening

Reactions to foods, like peanuts, can be different. It all depends on the person — and sometimes the same person can react differently at different times.

How Is an Allergic Reaction Treated?

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 get worse, leading someone to have trouble breathing, feel lightheaded, or to pass out. If it is not treated right away, anaphylaxis can be life-threatening.

If you have a peanut allergy (or any kind of serious food allergy), the doctor will want you to carry an epinephrine auto-injector in case of an emergency.

An epinephrine (pronounced: eh-puh-NEH-frin) auto-injector is a prescription medicine that comes in a small, easy-to-carry container. It's easy to use. Your doctor will show you how. Keep the epinephrine with you, not in a locker or in the nurse's office.

Every second counts in an allergic reaction. If you start having serious allergic symptoms, like swelling of the mouth or throat or trouble breathing, use the epinephrine auto-injector right away. Also use it right away if your symptoms involve two different parts of the body, like hives with vomiting. Then call 911 and have someone take you to the emergency room. You need to be under medical supervision because even if the worst seems to have passed, a second wave of serious symptoms can happen.

The doctor can also give you an allergy action plan, which helps you prepare for, recognize, and treat an allergic reaction. Share the plan with anyone else who needs to know, such as relatives, school officials, and coaches. Also consider wearing a medical alert bracelet.

Keeping epinephrine on hand at all times should be just part of your action plan. It's also a good idea to carry an over-the-counter (OTC) antihistamine as this can help treat mild allergy symptoms. But never use as a replacement for epinephrine shot in life-threatening reactions. Always use the epinephrine shot as the first treatment.

Living With Peanut Allergy

If allergy skin testing shows that you have a peanut allergy, an will provide guidelines on what to do.

The best way to prevent a reaction is to avoid peanuts. This means more than just not eating them. It also means not eating any foods that might contain peanuts as ingredients.

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

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

• "may contain peanuts"
• "produced on shared equipment with tree nuts or peanuts"

People who are allergic to nuts should avoid foods with these statements on the label. Although these foods might not use peanut 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." This is when nuts get into a food product because it is made or served in a place that uses nuts in other foods. Manufacturers are not required to list peanuts on the label when there might be accidental cross-contamination, but many do.

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

• Cookies and baked goods. Even if baked goods don't contain nut ingredients, it is possible that they came into contact with peanuts 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, water ice, and yogurt shops because the same dispensing machine and utensils are 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, Chinese, and Indian) foods often contain peanuts. 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 be cautious. 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 with nuts. Because ingredients can change, it's important to read the label every time, even if the food was safe in the past. And two foods that seem the same might also have differences in how they're made.

What Else Should I Know?

Here are other things to remember:

• 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.
• 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 peanut allergy. If the manager, chef, or owner of a restaurant is uncomfortable about your request for peanut-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 medicine (including epinephrine) on hand at all times — not in your locker, but in a pocket, purse, or bookbag that's always with you.

Living with a food allergy 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 food 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!

For more about managing food allergies, visit:

• Food Allergy Research & Education (FARE)