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:
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 your child has a tree nut allergy (or any kind of serious food allergy), always keep two epinephrine auto-injectors available in case of a severe reaction.
An epinephrine 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. Kids who are old enough can be taught how to give themselves the injection. If they carry the epinephrine, it should be nearby, not left in a locker or in the nurse's office.
The doctor can also give you an allergy action plan, which helps you prepare for, recognize, and treat an allergic reaction. Share it with anyone who takes care of your child, including relatives, school officials, and parents at playdates. Also consider having your child wear a medical alert bracelet.
Every second counts in an allergic reaction. If your child starts having serious allergic symptoms, like swelling of the mouth or throat or trouble breathing, give the epinephrine auto-injector right away. Also give it right away if the symptoms involve two different parts of the body, like hives with vomiting. Then call 911 and take your child to the emergency room. Your child needs to be under medical supervision because even if the worst seems to have passed, a second wave of serious symptoms can happen.
Sometimes allergists recommend also carrying over-the-counter (OTC) , as these can help treat mild allergy symptoms. Use an antihistamine after — not as a replacement for — the epinephrine shot during a life-threatening reaction.
What Else Should I Know?
If your child has a tree nut allergy, help them avoid eating tree nuts. Read food labels carefully because ingredients can change, and tree nuts can be found in unexpected places.
The best way to be sure a food is nut-free is to read the food label. Manufacturers of foods sold in the United States must state on their labels whether the foods contain tree nuts. Check the ingredients list first.
Some foods look OK from the ingredient list, but while being made they can have contact with tree nuts. This is called cross-contamination. Look for advisory statements such as "May contain tree nuts," "Processed in a facility that also processes tree nuts," or "Manufactured on equipment also used for tree nuts." Not all companies label for cross-contamination, so if in doubt, call or email the company to be sure.
Some of the highest-risk foods for people with a tree nut allergy include baked goods, candy, sauces, and ice cream. Also be on the lookout for shared equipment, such as ice cream scoops or soft-serve dispensing machines.
When eating away from home, make sure your child always has two epinephrine auto-injectors with them that haven’t expired. Also, tell the people preparing or serving your child's food about the nut allergy. Sometimes, you may want to bring food with you that you know is safe. Don't eat at the restaurant if the chef, manager, or owner seems uncomfortable with your request for a safe meal.
Also talk to the staff at school about cross-contamination risks for foods in the cafeteria. Some families feel most comfortable packing lunches from home.