Food allergy

A food allergy is an immune system reaction to certain foods. Even a tiny amount of an allergy-causing food can trigger symptoms such as itching, rashes, upset stomach and wheezing. In some people, a food allergy can cause a life-threatening reaction known as anaphylaxis.

Food allergy affects an estimated 10% of the general population and about 8% of children.

Treatment plans include education to avoid allergy-causing foods. Medicines can help lessen symptoms or prevent reactions to accidental exposure. Life-saving medicine is needed if a person experiences anaphylaxis.

A food allergy is different from food intolerance. Both conditions may have similar digestive symptoms. But a food intolerance is not an immune system reaction. Instead, this condition happens when the body can't digest certain foods or use certain nutrients.

Food allergy symptoms usually start within a few minutes to two hours after eating the allergy-causing food. The seriousness of symptoms can vary widely. The symptoms may range from mild to life-threatening.

The most common food allergy symptoms include:

• A rash, itchiness, raised patches on the skin or swollen skin.
• Itching or swelling of the lips, face, tongue and throat.
• Watery, itchy or swollen eyes.
• Belly pain, upset stomach, diarrhea or vomiting.
• Stuffy or runny nose.
• Wheezing, coughing or trouble breathing.
• Dizziness, lightheadedness or fainting.

Anaphylaxis

A food allergy can trigger a severe allergic reaction called anaphylaxis. This can cause life-threatening signs and symptoms, including:

• Tightening of the airways.
• A swollen throat or the sensation of a lump in your throat that makes it hard to breathe.
• A drop in blood pressure.
• Rapid pulse.
• Confusion or other changes in mental status.
• Dizziness, lightheadedness or loss of consciousness.

Emergency treatment is critical for anaphylaxis. Untreated, anaphylaxis can be fatal.

When to see a doctor

See a healthcare professional or allergist if you have food allergy symptoms shortly after eating. If possible, see a health professional when the allergic reaction is occurring. This can help with a diagnosis.

Get emergency care if you have signs or symptoms of anaphylaxis.

A food allergy happens when the immune system reacts to food as if it were reacting to a germ or parasite. The immune system creates antibodies to a certain protein in a food item, such as a peanut.

If a person is allergic to peanuts, the antibodies in the blood find and attach themselves to these peanut proteins. This antibody activity sends a signal for the immune system to mount an attack. The signs and symptoms of a food allergy are the result of the immune system fighting what it thinks is a foreign substance.

A food that causes an allergic reaction is called an allergen. The most common food allergens include:

• Cow's milk.
• Chicken eggs.
• Peanuts.
• Tree nuts, such as walnuts and pecans.
• Shellfish, such as shrimp, lobster, scallops and crab.
• Fish.
• Wheat.
• Soy.

Pollen-food allergy syndrome

People who are allergic to certain pollens may be allergic to certain raw plant foods. But people usually have no reaction if the food is cooked or processed. This condition is called pollen-food allergy syndrome or oral allergy syndrome. The following plant allergens are linked to possible food allergies.

Birch pollen. If you are allergic to birch pollen, you also may have a reaction to several foods.

Fruits

• Apple
• Apricot
• Cherry
• Peach
• Pear
• Plum

Nuts and legumes

• Almond
• Hazelnut
• Peanut
• Soybean

Herbs and seeds

• Aniseed
• Caraway seed
• Coriander
• Fennel
• Parsley

Vegetables

• Carrot
• Celery

Ragweed pollen. If you are allergic to ragweed pollen, you also may have a reaction to some foods.

• Banana
• Cantaloupe
• Cucumber
• Honeydew
• Watermelon
• Zucchini

Grass pollens. If you are allergic to grass pollens, you also may be allergic to several foods.

Fruits

• Cantaloupe
• Honeydew
• Kiwi
• Orange
• Tomato
• Watermelon

Legumes

• Peanut

Vegetables

• Swiss chard
• White potato

Mugwort pollen. If you are allergic to mugwort pollen, you also may be allergic to several foods:

Fruits

• Bell pepper
• Grape
• Peach
• Lychee
• Mango

Herbs and seeds

• Aniseed
• Black pepper
• Caraway seed
• Coriander
• Fennel
• Paprika
• Mustard
• Parsley
• Sunflower seeds

Vegetables

• Broccoli
• Cabbage
• Carrot
• Cauliflower
• Celery
• Garlic
• Onion

Exercise-induced food anaphylaxis

Some people may experience an anaphylactic allergic reaction if they do moderate or strenuous exercise a few hours after eating certain foods. Most commonly this happens after eating wheat or shellfish. If these people don't exercise after eating the allergen, they don't have an allergic reaction.

Other reactions

Other reactions to food may have symptoms similar to food allergies, but activities in the body other than immune system reactions are involved.

Food intolerance is when the body cannot digest certain foods or break down nutrients in foods. A food intolerance may cause digestive symptoms similar to allergic reactions:

• Excessive gas.
• Bloating.
• Cramping or stomach pain.
• Diarrhea.

Examples of food intolerance include:

• Lactose intolerance is the result of the body not being able to break down the main sugar in milk called lactose.
• Gluten sensitivity is the result of the body not being able to break down a protein called gluten that is in wheat, barley and rye.

Food poisoning is a sickness people get from something they ate or drank. The causes are germs or other substances in the food or drink. Symptoms most often start within hours or days of eating the food.

Sensitivity to additives in certain foods can cause symptoms similar to allergic reactions. For example, sulfites used to preserve dried fruit, canned goods and wine can trigger asthma attacks in people with severe asthma.

Celiac disease is an immune system reaction to gluten, but it's a unique reaction that's different from a typical food allergy. It does not cause anaphylaxis. The immune system reaction to gluten causes damage to the small intestine and leads to an inability to absorb certain nutrients.

Food allergy risk factors include:

• Family history. Having a family member with any allergy is a key risk factor for food allergies.
• Other allergies. An allergy to one food increases the risk of becoming allergic to another food. Having other allergies, such as hay fever, also increases the risk of food allergies.
• Age. Food allergies commonly begin during childhood, especially during the infant and toddler years. Children typically outgrow allergies to milk, soy, wheat and eggs. Severe food allergies and allergies to peanuts, tree nuts and shellfish are more likely to be lifelong.
• Atopic dermatitis. Atopic dermatitis, also called eczema, is a condition that causes dry and itchy skin, rashes, thickened skin, and other symptoms. Having this condition in early childhood increases the risk of having food allergies.
• Asthma. Asthma and food allergy commonly occur together. When they do, both food allergy and asthma symptoms are more likely to be severe.

Introducing peanut products and eggs early in childhood may lower the risk of allergy to peanuts and eggs. Studies have shown that introducing these foods in the diet of children 4 to 11 months of age lessens the likelihood of having peanut and egg allergies later. Studies of early introduction of other common food allergens have not shown that this lowers risk.

Before introducing common allergy-related foods, talk with your child's healthcare team about the best time to offer them.

Children with pets or who grow up around livestock on a farm may have a lower risk of food allergies.

Your healthcare professional does a complete physical exam and asks a number of questions about:

• Symptoms.
• Diet.
• Foods that seem related to symptoms.
• The timing from eating a food to having symptoms.
• Family history of allergies.

Allergy tests

Allergy tests can help your healthcare team find foods that may cause an allergic reaction. A negative result means that you may not be allergic to a particular food. A positive result means that you may be allergic to that food.

The results show whether your body has antibodies to a food allergen. They don't necessarily show that you will actually have an allergic reaction to the food. The test results can help your healthcare team figure out how likely you are to be allergic to a food and how to move forward with more tests or treatments.

Allergy tests include:

• Skin prick test. A small amount of the suspected food is placed on the skin of your forearm or back. A healthcare professional then pricks your skin to allow a tiny amount of the substance beneath your skin surface. If your body has antibodies to that food allergen, a raised bump appears.
• Blood tests. Laboratory tests of a blood sample can identify the presence of antibodies to a particular food allergen.

Oral food challenge

This test is done with a healthcare team that has experience with interpreting the reactions to the test and treating the symptoms. There is a risk of anaphylaxis, which must be treated immediately.

For two weeks before the test, the suspect food isn't eaten. No food is eaten for two hours before the test. You may be asked not to take certain medicines.

During this test, you're given small but increasing amounts of the food suspected of causing your symptoms. An allergic reaction confirms that you are allergic to that food. If you don't have a reaction, you may be able to include this food in your diet.

The primary approach to food allergy is to strictly avoid the food that causes the allergic reaction. But you may need treatment if you come in contact with the food allergen or accidentally eat it

Anaphylaxis treatment

Many people with food allergies are prescribed an epinephrine autoinjector (Adrenaclick, EpiPen, others). This device is a combined syringe and concealed needle that injects a single dose of medicine when pressed against your thigh. Review how and when to use an epinephrine autoinjector with your healthcare professional.

Epinephrine also may be taken as a nasal spray. The brand name for the spray version is Neffy.

If you've been prescribed epinephrine:

• Be sure you know how to use epinephrine. Also, make sure the people closest to you know how to give the medicine. If they're with you in an anaphylactic emergency, they may need to give you a dose.
• Carry epinephrine with you at all times. It may be hard to predict when an accidental exposure may trigger an anaphylactic reaction.
• Always be sure to replace epinephrine before its expiration date, or it may not work properly.
• Work with your child's school. It's important to work with nurses, teachers and other school staff so they understand your child's need for epinephrine. Create an anaphylaxis action plan.

One of the keys to preventing an allergic reaction is to completely avoid the food that causes your symptoms.

• Read food labels to make sure they don't have an ingredient you're allergic to. Food labels must clearly list whether the food products have any common food allergens. Also, check the label to see if the food was made in a setting where the food allergen also is prepared.
• Plan meals and snacks before leaving home. If necessary, take a cooler packed with allergen-free foods when you travel or go to an event. If you or your child can't have the cake or other dessert at a party, bring an approved special treat so no one feels left out of the celebration.
• Wear a medical alert bracelet or necklace. These bracelets and necklaces let others know that you have a food allergy if you have a reaction and you cannot communicate.
• Be careful at restaurants. Be certain your server or chef is aware that you absolutely can't eat the food you're allergic to. Also, make sure food isn't prepared on surfaces or in pans that contained the food you're allergic to.
• When in doubt, say no thanks. At restaurants and social gatherings, there's often a risk of being exposed to a food allergen. People may not understand that a food allergy is serious or that a tiny amount of food can cause a severe reaction.

If your child has a food allergy, work with your child, family members, sitters, teachers, coaches, and others who care for or supervise your child.

• Explain food allergy symptoms. Teach the adults who spend time with your child how to recognize signs and symptoms of an allergic reaction. Emphasize that an allergic reaction can be life-threatening and requires immediate action.
• Educate your child. Talk with your child about what foods to avoid. Make sure your child also knows to ask for help right away in case of a food reaction. Make sure an older child knows how to take epinephrine.
• Write an action plan. Your plan should describe what steps to take if your child has an allergic reaction to food. Make sure it states how and when to use an epinephrine autoinjector or nasal spray and when to get emergency care. Provide a copy of the plan to your child's school nurse, classroom teacher, coaches and others who provide supervision.
• Have your child wear a medical alert bracelet or necklace. This alert lists your child's allergy symptoms and explains how others can provide first aid in an emergency.
• Talk about food avoidance. Talk with caregivers and teachers about classroom practices of hand-washing and cleaning of surfaces that can help prevent exposure to allergens.

A food allergy can be a source of ongoing concern that affects life at home, school and work. Daily activities that are easy for most families, such as grocery shopping and meal preparation, can become stressful for families and caregivers living with food allergies.

Keep these strategies in mind to help manage your or your child's food allergy-related stress:

• Connect with others. The opportunity to discuss food allergies and exchange information with others who share your concerns can be very helpful. Many internet sites and nonprofit organizations offer information and forums for discussing food allergies. The Food Allergy Research & Education (FARE) website can direct you to support groups and events in your area.
• Address bullying. Children are sometimes bullied at school because of their food allergies. Discussing your child's allergy with school personnel greatly reduces your child's risk of being a bullying target.

Because appointments can be brief, and because there's often a lot of ground to cover, it's a good idea to be well prepared. Here's some information to help you get ready and know what to expect.

• Write down any symptoms you've had, including any that may seem unrelated to your concerns about food.
• Write down key personal information, including any major stresses or recent life changes.
• Make a list of all medicines, vitamins and supplements that you or your child is taking, as well as the doses and reasons for taking each one.
• Take a family member or friend along, if possible. Sometimes it can be difficult to remember all the information provided to you during an appointment. Someone who accompanies you may recall something that you missed or forgot.
• Write down questions to ask your care team.

Your time is limited, so preparing a list of questions will help you make the most of your time together. List your questions from most important to least important in case time runs out. Some basic questions to ask include:

• Are my symptoms likely caused by a food allergy or another condition?
• What kinds of tests do I need?
• Is my condition likely temporary or long-lasting?
• What types of treatment are available?
• I have other health conditions. How can I best manage these conditions together?
• Should I see a specialist? What will that cost, and will my insurance cover seeing a specialist?
• Is there a generic alternative to the medicine you're prescribing me?
• Do you have any printed material that I can take home with me? What websites do you recommend visiting?

If your child is seeing the health professional for a food allergy, you also may want to ask:

• Is my child likely to outgrow this allergy?
• Are there alternatives to the food or foods that trigger my child's allergy symptoms?
• How can I help keep my child with a food allergy safe at school?

In addition to the questions that you've prepared to ask your healthcare professional, don't hesitate to ask other questions during your appointment.

What to expect from your doctor

Your healthcare professional is likely to ask you a few questions. Being ready to answer them may save time to go over any points you want to spend more time on. You may be asked:

• What were your symptoms?
• How long did symptoms last?
• What did you eat before the reaction?
• How long did it take symptoms to appear after eating suspect food?
• How much food did you eat before the reaction?
• Was the suspect food cooked or raw?
• Do you know how the food was prepared?
• Have you eaten the suspect food in the past without a reaction?
• Did you take any allergy medicines you can buy without a prescription such as antihistamines?
• Do you or someone else in the family have allergies or asthma?

What you can do in the meantime

If you suspect you have a food allergy, avoid the food altogether until your appointment. If you do eat the food and have a mild reaction, antihistamines you can buy without a prescription may help relieve symptoms. If you have a more severe reaction and any symptoms of anaphylaxis, seek emergency help.