When someone has a tree nut allergy, the body's immune system, which normally fights infections, overreacts to proteins in tree nuts. If the person drinks or eats a product that contains tree nuts, the body thinks these proteins are harmful invaders. The immune system responds by working very hard to fight off the invader. This causes an allergic reaction.
There are many different tree nuts, including almonds, Brazil nuts, walnuts, hazelnuts, macadamia nuts, pistachios, pecans, and cashews. Some people are allergic to just one, while some are allergic to several, or all.
Sometimes people outgrow some food allergies over time, but tree nut allergies are lifelong in many people.
What Are the Signs & Symptoms of a Tree Nut Allergy?
If someone with a tree nut allergy eats or drinks something with tree nuts in it, the body releases chemicals like , which can cause symptoms such as:
itchy, watery, or swollen eyes
a drop in blood pressure, causing lightheadedness or loss of consciousness (passing out)
anxiety or a feeling that something bad is happening
Allergic reactions to nuts can differ. 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.
Tree nut allergy can cause a severe reaction called anaphylaxis, even if a previous reaction was mild. Anaphylaxis might start with some of the same symptoms as a less severe reaction, but can quickly get worse. The person may have trouble breathing or pass out. More than one part of the body might be involved. If it isn't treated, anaphylaxis can be life-threatening.
How Is an Allergic Reaction Treated?
If you have a tree nut 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 an epinephrine shot in life-threatening reactions. Always use the epinephrine shot as the first treatment.
Living With Tree Nut Allergy
If allergy skin testing shows that you have a tree nut allergy, an will provide guidelines on what to do.
The best way to prevent a reaction is to avoid tree nuts. Avoiding nuts means more than just not eating them. It also means not eating any foods that might contain tree nuts 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 tree nuts. Check the ingredients list first.
After checking the ingredients list, look on the label for phrases like these:
"may contain tree nuts"
"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 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." 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 tree nuts on the label when there might be accidental cross-contamination, but many do.
Some of the highest-risk foods for people with a 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 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, 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 tree nuts. Mexican and Mediterranean foods may also use nuts, so the risk of cross-contamination is high with these foods.
Sauces. Some cooks use nuts 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 almond butter sandwiches is not used to butter your bread and that nut breads are not toasted in the same toaster you use.
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, chef, or owner of a restaurant is uncomfortable about your request for 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 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 almond 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!