Food Allergy

An Overview

NIAID

National Institute of Allergy and Infectious Diseases

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

National Institutes of Health

NIAID HEALTH INFORMATION

National Institute of Allergy and Infectious Diseases

Food Allergy

An Overview

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

National Institutes of Health

National Institute of Allergy and Infectious Diseases

NIH Publication No. 12-5518 

July 2012

www.niaid.nih.gov

1NIAID I FOOD ALLERGY

Contents

3 Introduction

4 What Is Food Allergy?

5 What Is an Allergic Reaction to Food?

8 What Is Anaphylaxis?

10 Common Food Allergies in Infants, Children, and Adults

12 Milk Allergy in Infants and Children

14 Is It Food Allergy or Food Intolerance?

17 Diagnosing Food Allergy

22 Preventing and Treating Food Allergy

24 Food Allergy Research at NIAID

26 Glossary

29 More Information

33 Credits

NIAID I FOOD ALLERGY

3

Introduction

All of us eat to survive, and most of us enjoy eating. However, 

recent studies have found that almost 1 in 20 young children 

under the age of 5 years and almost 1 in 25 adults are allergic 

to at least one food. Other studies indicate that food allergy, 

especially allergy to peanut, is on the rise. As a result, more and 

more people are becoming aware of food allergy, making it a 

subject of increasing public concern.

When one person in a family has a food allergy, the whole 

family is affected. There may be day-to-day anxiety that a loved 

one may accidentally eat a food that could lead to anaphylaxis,

a dangerous allergic reaction.

This booklet will help you understand allergic reactions to 

foods and their possible causes, and it explains how a healthcare 

professional diagnoses and treats food allergy.

If you suspect you or a member of your family have a food 

allergy, consult your healthcare professional for medical advice.

Note: Words in bold are defined in the glossary at the end of this booklet.
4 NIAID I FOOD ALLERGY

What Is Food Allergy?

Food allergy is an abnormal response to a food triggered by 

the body’s immune system. There are several types of immune 

responses to food. This booklet focuses on one type of adverse 

reaction to food—that in which the body produces a specific 

type of antibody called immunoglobulin E (IgE).

The binding of IgE to specific molecules present in a food 

triggers the immune response. The response may be mild or 

in rare cases it can be associated with the severe and lifethreatening reaction called anaphylaxis, which is described 

in a later section of this booklet. Therefore, if you have a 

food allergy, it is extremely important for you to work with 

your healthcare professional to learn what foods cause your 

allergic reaction.

Sometimes, a reaction to food is not an allergy at all but another 

type of reaction called food intolerance. A description of food 

intolerance appears later in this booklet.
5NIAID I FOOD ALLERGY

What Is an Allergic Reaction 

to Food?

A food allergy occurs when the immune system responds to a 

harmless food as if it were a threat. The first time a person with 

food allergy is exposed to the food, no symptoms occur; but the 

first exposure primes the body to respond the next time. When 

the person eats the food again, an allergic response can occur.

WHAT IS A FIRST EXPOSURE TO FOOD?

Usually, the way you are first exposed to a food 

is when you eat it. But sometimes a first exposure 

or subsequent exposure can occur without your 

knowledge.

This may be true in the case of peanut allergy. A 

person who experiences anaphylaxis on the first 

known exposure to peanut may have previously

•	Touched peanuts

•	Used a peanut-containing skin care product

•	Breathed in peanut dust in the home or when 

close to other people eating peanuts

The Allergic Reaction Process

An allergic reaction to food is a two-step process.

Step 1: The first time you are exposed to a food allergen, your 

immune system reacts as if the food were harmful and makes 

specific IgE antibodies to that allergen. The antibodies circulate 

through your blood and attach to mast cells and basophils. 

Mast cells are found in all body tissues, especially in areas of 

your body that are typical sites of allergic reactions. Those sites 

include your nose, throat, lungs, skin, and gastrointestinal (GI) 

tract. Basophils are found in your blood and also in tissues that 

have become inflamed due to an allergic reaction. 
6 NIAID I FOOD ALLERGY

Step 2: The next time you are exposed to the same food allergen, 

it binds to the IgE antibodies that are attached to the mast cells 

and basophils. The binding signals the cells to release massive 

amounts of chemicals such as histamine. Depending on the 

tissue in which they are released, these chemicals will cause you 

to have various symptoms of food allergy. The symptoms can 

range from mild to severe. A severe allergic reaction can include 

a potentially life-threatening reaction called anaphylaxis.

Generally, you are at greater risk for developing a food allergy 

if you come from a family in which allergies are common. 

These allergies are not necessarily food allergies but perhaps 

other allergic diseases, such as asthma, eczema (atopic 

dermatitis), or allergic rhinitis (hay fever). If you have two 

parents who have allergies, you are more likely to develop 

food allergy than someone with one parent who has allergies.

An allergic reaction to food usually takes place within a few 

minutes to several hours after exposure to the allergen. The 

process of eating and digesting food and the location of mast 

cells both affect the timing and location of the reaction.

Symptoms of Food Allergy

If you are allergic to a particular food, you may experience all 

or some of the following symptoms:

•	 Itching in your mouth

•	 Swelling of lips and tongue

•	 GI symptoms, such as vomiting, diarrhea, or abdominal 

cramps and pain

•	 Hives

•	 Worsening of eczema

•	 Tightening of the throat or trouble breathing

•	 Drop in blood pressure
7NIAID I FOOD ALLERGY

EOSINOPHILIC ESOPHAGITIS

Eosinophilic esophagitis (EoE) is a newly recognized chronic 

disease that can be associated with food allergies. It is increasingly 

being diagnosed in children and adults.

Symptoms of EoE include nausea, vomiting, and abdominal pain 

after eating. A person may also have symptoms that resemble acid 

reflux from the stomach. In older children and adults, it can cause 

more severe symptoms, such as difficulty swallowing solid food or 

solid food sticking in the esophagus for more than a few minutes. 

In infants, this disease may be associated with failure to thrive.

If you are diagnosed with EoE, you will probably be tested for 

allergies. In some situations, avoiding certain food allergens will 

be an effective treatment for EoE.

CROSS-REACTIVE FOOD ALLERGIES

If you have a life-threatening reaction to a certain food, your 

healthcare professional will show you how to avoid similar foods 

that may trigger this reaction. For example, if you have a history 

of allergy to shrimp, allergy testing will usually show that you are 

also allergic to other shellfish, such as crab, lobster, and crayfish. 

This is called cross-reactivity.
8 NIAID I FOOD ALLERGY

What Is Anaphylaxis?

If you have a food allergy, there is a chance that you may 

experience a severe form of allergic reaction known as 

anaphylaxis. Anaphylaxis may begin suddenly and may lead 

to death if not immediately treated.

Anaphylaxis includes a wide range of symptoms that can occur 

in many combinations. Some symptoms are not life-threatening, 

but the most severe restrict breathing and blood circulation.

Many different parts of your body can be affected.

•	 Skin—itching, hives, redness, swelling

•	 Nose—sneezing, stuffy nose, runny nose

•	 Mouth—itching, swelling of lips or tongue

•	 Throat—itching, tightness, difficulty swallowing, hoarseness

•	 Chest—shortness of breath, cough, wheeze, chest pain, tightness

•	 Heart—weak pulse, passing out, shock

•	 GI tract—vomiting, diarrhea, cramps

•	 Nervous system—dizziness or fainting

Symptoms may begin within several minutes to several hours 

after exposure to the food. Sometimes the symptoms go away, 

only to return 2 to 4 hours later or even as many as 8 hours 

later. When you begin to experience symptoms, you must seek 

immediate medical attention because anaphylaxis can be lifethreatening.

Anaphylaxis caused by an allergic reaction to a certain food is 

highly unpredictable. The severity of a given attack does not 

predict the severity of subsequent attacks. The response will 

vary depending on several factors, such as
NIAID I FOOD ALLERGY

9

•	 Your sensitivity to the food

•	 How much of the food you are exposed to

•	 How the food enters your body

Any anaphylactic reaction may become dangerous and must be 

evaluated by a healthcare professional.

Food allergy is the leading cause of anaphylaxis. However, 

medications, insect stings, and latex can also cause an allergic 

reaction that leads to anaphylaxis.

HOW DO YOU KNOW IF A PERSON IS HAVING 

AN ANAPHYLACTIC REACTION?

Anaphylaxis is highly likely if at least one of the following three 

conditions occurs:

1. Within minutes or several hours of the onset of an illness, a 

person has skin symptoms (redness, itching, hives) or swollen 

lips and either

•	Difficulty breathing, or

•	A drop in blood pressure

2. A person was exposed to an allergen likely to cause an allergic 

reaction, and, within minutes or several hours, two or more of 

the following symptoms occur:

•	Skin symptoms or swollen lips

•	Difficulty breathing

•	A drop in blood pressure

•	GI symptoms such as vomiting, diarrhea, or cramping

3. A person exposed to an allergen previously known to cause 

an allergic reaction in that person experiences a drop in blood 

pressure.
10NIAID I FOOD ALLERGY

Common Food Allergies in Infants, 

Children, and Adults

In infants and children, the most common foods 

that cause allergic reactions are

•	 Egg

•	 Milk

•	 Peanut

•	 Tree nuts such as walnuts

•	 Soy (primarily in infants)

•	 Wheat

In adults, the most common foods that cause 

allergic reactions are

•	 Shellfish such as shrimp, crayfish, lobster, 

and crab

•	 Peanut

•	 Tree nuts

•	 Fish such as salmon

Food allergies generally develop early in life but can develop at 

any age. For example, milk allergy tends to develop early in life, 

whereas shrimp allergy generally develops later in life.

Children usually outgrow their egg, milk, and soy allergies, 

but people who develop allergies as adults usually have their 

allergies for life. Children generally do not outgrow their 

allergy to peanut.
11NIAID I FOOD ALLERGY

Finally, foods that are eaten routinely increase the likelihood 

that a person will develop allergies to that food. In Japan, for 

example, rice allergy is more frequent than in the United States, 

and in Scandinavia, codfish allergy is more common than in the 

United States.

ORAL ALLERGY SYNDROME

Oral allergy syndrome (OAS) is an allergy to certain raw fruits 

and vegetables, such as apples, cherries, kiwis, celery, tomatoes, 

and green peppers. OAS occurs mostly in people with hay fever, 

especially spring hay fever due to birch pollen and late summer 

hay fever due to ragweed pollen.

Eating the raw food causes an itchy, tingling sensation in the 

mouth, lips, and throat. It can also cause swelling of the lips, 

tongue, and throat; watery, itchy eyes; runny nose; and sneezing. 

Just handling the raw fruit or vegetable may cause a rash, itching, 

or swelling where the juice touches the skin.

Cooking or processing easily breaks down the proteins in the 

fruits and vegetables that cause OAS. Therefore, OAS typically 

does not occur with cooked or baked fruits and vegetables or 

processed fruits, such as in applesauce. 
12NIAID I FOOD ALLERGY

Milk Allergy in Infants 

and Children

Allergy to cow’s milk is common in infants and young children 

and can develop within days to months of birth. 

In children, allergy to cow’s milk can cause abdominal pain, 

hives, and eczema. These symptoms are typically associated 

with IgE antibodies to milk. Because abdominal pain is also 

a symptom of lactose intolerance (see page 14), only your 

healthcare professional can determine whether your child’s 

symptoms are caused by an allergic reaction to cow’s milk. 

In other children, cow’s milk can lead to a different type of 

reaction to milk, resulting in colic and sleeplessness, as well as 

blood in the stool and poor growth. This type of reaction to 

milk is associated with immune responses that are not related 

to IgE antibody.
13NIAID I FOOD ALLERGY

FOOD ALLERGY: PREGNANCY, BREASTFEEDING, 

AND INTRODUCING SOLID FOODS TO YOUR BABY

Healthcare experts still do not have enough 

conclusive evidence to tell pregnant women, 

nursing mothers, and mothers of infants 

how to prevent food allergy from developing 

in their children. Be sure to talk with your 

healthcare professional before changing your 

diet or your baby’s diet.

Here is what healthcare experts know now:

Pregnancy

•	When you are pregnant, you should eat a balanced diet.

•	If you are allergic to a food, you should avoid it. 

•	If you are not allergic to foods—such as egg, tree nuts, peanut, 

fish, or cow’s milk (all highly allergenic), you should not avoid 

them because there is no conclusive evidence that avoiding 

these foods will prevent food allergy from developing in your 

infant in the future.

Breastfeeding

•	Healthcare experts recommend that mothers feed their babies 

only breast milk for the first 4 months of life because of the 

health benefits of breastfeeding.

•	Mothers who breastfeed do not need to avoid foods that 

are considered to be highly allergenic because there is no 

conclusive evidence that avoiding these foods will prevent 

food allergy from developing in their infants. 

Introducing Solid Foods

•	Healthcare experts in the United States currently suggest that 

you do not introduce solid food into your baby’s diet until 4 

to 6 months of age. 

•	There is no conclusive evidence to suggest that you should 

delay the introduction of solid foods beyond 4 to 6 months 

of age. 

•	There is no conclusive evidence to suggest that you should 

delay the introduction of the most common potentially 

allergenic foods (milk, egg, peanut) beyond 4 to 6 months 

of age. Delay will not prevent your child from developing 

an allergy in the future.
14NIAID I FOOD ALLERGY

Is It Food Allergy or 

Food Intolerance?

Food allergy is sometimes confused with food intolerance. 

To find out the difference between food allergy and food 

intolerance, your healthcare professional will go through a 

list of possible causes for your symptoms.

Types of Food Intolerance

Lactose intolerance

Lactose is a sugar found in milk and most milk products. 

Lactase is an enzyme in the lining of the gut that breaks down 

or digests lactose. Lactose intolerance occurs when lactase 

is missing. Instead of the enzyme breaking down the sugar, 

bacteria in the gut break it down, which forms gas, which 

in turn causes symptoms of bloating, abdominal pain, and 

sometimes diarrhea.

Lactose intolerance is uncommon in babies and young children 

under the age of 5 years. Because lactase levels decline as people 

get older, lactose intolerance becomes more common with 

age. Lactose intolerance also varies widely based on racial and 

ethnic background. 

Your healthcare professional can use laboratory tests to find out 

whether your body can digest lactose.

Food additives

Another type of food intolerance is a reaction to certain 

products that are added to food to enhance taste, add color, 

or protect against the growth of microbes. Several compounds 

such as MSG (monosodium glutamate) and sulfites are tied to 

reactions that can be confused with food allergy.
15NIAID I FOOD ALLERGY

•	 MSG is a flavor enhancer. When 

taken in large amounts, it can 

cause some of the following:

Flushing

Sensations of warmth

Headache

Chest discomfort

These passing reactions occur 

rapidly after eating large 

amounts of food to which MSG 

has been added.

•	 Sulfites are found in food for 

several reasons:

They have been added to 

increase crispness or prevent 

mold growth.

They occur naturally in the 

food.

They have been generated 

during the winemaking 

process.

Sulfites can cause breathing 

problems in people with asthma.

The Food and Drug 

Administration (FDA) has 

banned sulfites as spray-on 

preservatives for fresh fruits and 

vegetables. When sulfites are 

present in foods, they are listed 

on ingredient labels.
16NIAID I FOOD ALLERGY

Gluten intolerance

Gluten is a part of wheat, barley, and rye. Gluten intolerance 

is associated with celiac disease, also called gluten-sensitive 

enteropathy. This disease develops when the immune system 

responds abnormally to gluten. This abnormal response does 

not involve IgE antibody and is not considered a food allergy.

Food poisoning

Some of the symptoms of food allergy, such as abdominal 

cramping, are common to food poisoning. However, food 

poisoning is caused by microbes, such as bacteria, and bacterial 

products, such as toxins, that can contaminate meats and dairy 

products.

Histamine toxicity

Fish, such as tuna and mackerel that are not refrigerated 

properly and become contaminated by bacteria, may contain 

very high levels of histamine. A person who eats such fish may 

show symptoms that are similar to food allergy. However, this 

reaction is not a true allergic reaction. Instead, the reaction is 

called histamine toxicity or scombroid food poisoning.

Other

Several other conditions, such as ulcers and cancers of the GI 

tract, cause some of the same symptoms as food allergy. These 

symptoms, which include vomiting, diarrhea, and cramping 

abdominal pain, become worse when you eat.
17NIAID I FOOD ALLERGY

Diagnosing Food Allergy

Detailed History

Your healthcare professional 

will begin by taking a detailed 

medical history to find out 

whether your symptoms are 

caused by an allergy to specific 

foods, a food intolerance, or 

other health problems.

A detailed history is the most 

valuable tool for diagnosing 

food allergy. Your healthcare 

professional will ask you 

several questions and listen to 

your history of food reactions 

to decide whether the facts fit 

a diagnosis of food allergy.

Your healthcare professional is likely to ask some of the 

following questions:

•	 Did your reaction come on quickly, usually within minutes 

to several hours after eating the food? 

•	 Is your reaction always associated with a certain food?

•	 How much of this potentially allergenic food did you eat 

before you had a reaction? 

•	 Have you eaten this food before and had a reaction? 

•	 Did anyone else who ate the same food get sick? 

•	 Did you take allergy medicines, and if so, did they help? 

(Antihistamines should relieve hives, for example.)
18NIAID I FOOD ALLERGY

Diet Diary

Sometimes your healthcare professional can’t make a diagnosis 

based only on your history. In that case, you may be asked to 

keep a record of what you eat and whether you have a reaction. 

This diet diary contains more details about the foods you eat 

than your history. From the diary, you and your healthcare 

professional may be able to identify a consistent pattern in 

your reactions.

Elimination Diet

The next step some healthcare professionals use is a limited 

elimination diet, in which the food that is suspected of causing 

an allergic reaction is removed from your diet. For example, if 

you suspect you are allergic to egg, your healthcare professional 

will instruct you to eliminate this one food from your diet. The 

limited elimination diet is done under the direction of your 

healthcare professional.
19NIAID I FOOD ALLERGY

Skin Prick Test

If your history, diet diary, or elimination diet suggests a specific 

food allergy is likely, then an allergist will use the skin prick test 

to confirm the diagnosis. 

With a skin prick test, your healthcare professional uses a needle 

to place a tiny amount of food extract just below the surface 

of the skin on your lower arm or back. If you are allergic, there 

will be swelling or redness at the test site. This is a positive 

result. It means that there are IgE molecules on the skin’s mast 

cells that are specific to the food being tested.

The skin prick test is simple and relatively safe, and results are 

ready in minutes.

You can have a positive skin prick test to a food, however, 

without having an allergic reaction to that food. A healthcare 

professional often makes a diagnosis of food allergy when 

someone has both a positive skin prick test to a specific food and

a history of reactions that suggests an allergy to the same food.

(above) A person receiving a skin prick test.
20NIAID I FOOD ALLERGY

Blood Test

Instead of the skin prick test, your healthcare professional can 

take a blood sample to measure the levels of food-specific IgE 

antibodies.

As with skin prick testing, positive blood tests do not necessarily 

mean that you have a food allergy. Your healthcare professional 

must combine these test results with information about your 

history of reactions to food to make an accurate diagnosis of 

food allergy.

(above) Blood samples ready for testing.
21NIAID I FOOD ALLERGY

Oral Food Challenge

Caution: Because oral food challenges can cause a severe 

allergic reaction, they should always be conducted by a 

healthcare professional who has experience performing them.

An oral food challenge is the final method healthcare 

professionals use to diagnose food allergy. This method includes 

the following steps:

•	 Your healthcare professional gives you individual doses of 

various foods (masked so you do not know what food is 

present), some of which are suspected of starting an allergic 

reaction.

•	 Initially, the dose of food is very small, but the amount 

is gradually increased during the challenge.

•	 You swallow the individual dose.

•	 Your healthcare professional watches you to see whether a 

reaction occurs.

To prevent bias, oral food challenges are often done double 

blinded. In a true double-blind challenge, neither you nor your 

healthcare professional knows whether the substance you eat 

contains the likely allergen. Another medical professional has 

made up the individual doses. In a single-blind challenge, your 

healthcare professional knows what you are eating but you 

do not.

A reaction only to suspected foods and not to the other foods 

tested confirms the diagnosis of a food allergy.
22NIAID I FOOD ALLERGY

Preventing and Treating 

Food Allergy

Prevention

There is currently no cure for food allergies. You can only 

prevent the symptoms of food allergy by avoiding the allergenic 

food. After you and your healthcare professional have identified 

the food(s) to which you are sensitive, you must remove them 

from your diet.

Read food labels

You must read the list of ingredients on the label of each 

prepared food that you are considering eating. Many allergens, 

such as peanut, egg, and milk, appear in prepared foods you 

normally would not associate with those foods. 

Since 2006, U.S. food 

manufacturers have been 

required by law to list the 

ingredients of prepared 

foods. In addition, food 

manufacturers must use plain 

language to disclose whether 

their products contain any 

of the top eight allergenic 

foods—egg, milk, peanut, tree 

nuts, soy, wheat, shellfish, 

and fish. Be aware that some labels say “may contain.” For the 

most current food labeling information, visit www.fda.gov. 

Keep clean

Simple measures of cleanliness can remove most allergens 

from the environment of a person with food allergy. For 

example, simply washing your hands with soap and water 

will remove peanut allergens, and most household cleaners 

will remove allergens from surfaces.
23NIAID I FOOD ALLERGY

Treatment of a Food Allergy Reaction

Unintentional exposure

When you have food allergies, you must be 

prepared to treat an unintentional exposure. 

Talk to your healthcare professional and 

develop a plan to protect yourself in case of 

an unintentional exposure to the food. For 

example, you should

•	 Wear a medical alert bracelet or necklace

•	 Carry an auto-injector device containing 

epinephrine (adrenaline)

•	 Seek medical help immediately

Mild symptoms

Talk to your healthcare professional to find out what medicines 

may relieve mild food allergy symptoms that are not part of an 

anaphylactic reaction. However, be aware that it is very hard for 

you to know which reactions are mild and which may lead to 

anaphylaxis.

EXERCISE-INDUCED FOOD ALLERGY

Exercise-induced food allergy is a rare situation that requires more 

than simply eating food to start a reaction. This type of reaction 

occurs after someone eats a specific food before exercising. As 

exercise increases and body temperature rises

•	Itching and light-headedness start

•	Hives may appear

•	Anaphylaxis may develop

Some people have this reaction from many foods, and others have 

it only after eating a specific food.

Treating exercised-induced food allergy is simple—avoid eating 

for a couple of hours before exercising.

Crustacean shellfish, alcohol, tomatoes, cheese, and celery 

are common causes of exercise-induced food allergy reactions.
24NIAID I FOOD ALLERGY

Food Allergy Research at NIAID

The National Institute of Allergy and Infectious Diseases 

(NIAID) is the lead institute for food allergy research at the 

National Institutes of Health.

NIAID supports basic and preclinical research in allergy and 

immunology that provides an increasingly better understanding 

of the immune system and how, in certain people, food elicits 

an allergic reaction. 

NIAID also conducts clinical trials that are attempting to 

change the body’s immune response so that it does not trigger 

an allergic reaction to food. These trials are either prevention 

trials or treatment trials.

•	 Prevention trials attempt to prevent allergies from developing 

in young children who are not yet allergic to a food.

•	 Treatment trials try to train the immune systems of people 

who are already allergic to a food not to react to the 

specific food.

Both treatment and prevention strategies attempt to induce a 

state of immunological tolerance to a food.

Current food allergy clinical trials funded by NIAID can be 

found on the Web site ClinicalTrials.gov by searching for 

“NIAID” and “food allergy.”

To learn more about food allergy-related research, go to 

NIAID’s Food Allergy Health Topic at www.niaid.nih.gov/

topics/foodallergy.
25NIAID I FOOD ALLERGY

GUIDELINES FOR THE DIAGNOSIS AND MANAGEMENT 

OF FOOD ALLERGY 

NIAID organized the development of the “Guidelines for the 

Diagnosis and Management of Food Allergy in the United States: 

Report of the NIAID-Sponsored Expert Panel.” These guidelines 

are intended for use by healthcare professionals to diagnose and 

manage patients with food allergies and related conditions such as 

eczema (atopic dermatitis), asthma, and eosinophilic esophagitis. 

The guidelines can be viewed and downloaded from the NIAID 

Web site at www.niaid.nih.gov/topics/foodallergy/clinical. A 

version of the guidelines for the general public is also available on 

the NIAID Web site.
26NIAID I FOOD ALLERGY

Glossary

allergen—a substance that causes an allergic reaction.

allergenic—describes a substance that produces an allergic 

reaction.

anaphylaxis—a severe reaction to an allergen that may lead 

to death.

antibody—a protein molecule tailor-made by the immune 

system to detect and help destroy invaders, such as bacteria, 

viruses, and toxins.

bacteria—single-celled microbes that have no nucleus. 

Some bacteria are potentially disease causing.

basophils—white blood cells that contribute to allergic 

inflammatory reactions.

celiac disease—an autoimmune disease of the digestive system 

that damages the small intestine and interferes with the 

absorption of the nutritional content of food. People who 

have celiac disease cannot tolerate gluten (a protein in wheat, 

rye, and barley).

eczema—the term for a group of allergic conditions that causes 

the skin to become inflamed and is characterized by redness, 

itching, and oozing lesions that become crusty. The most common 

type of eczema is known as atopic dermatitis, or atopic eczema, 

and is particularly common in young children and infants.

elimination diet—removal of certain foods from a person’s diet.

enzyme—a protein produced by living cells that promotes 

specific biochemical reactions.
27NIAID I FOOD ALLERGY

epinephrine—a hormone, also called adrenaline, that works 

rapidly to constrict blood vessels, preventing them from 

leaking fluid. It also relaxes airways, relieves cramping in the 

gastrointestinal tract, decreases swelling, and blocks itching and 

hives. Epinephrine is the drug in an EpiPen used to counter an 

anaphylactic reaction.

esophagus—the passageway through which food moves from 

the throat to the stomach.

extract—a liquid preparation containing food allergens from 

specific foods.

gastrointestinal (GI) tract—the organ system of the body that 

includes the esophagus, stomach, and small and large intestines.

histamine—a chemical stored in the granules of mast cells and 

basophils prior to release.

histamine toxicity—a reaction, which resembles an allergic 

reaction, to eating foods containing high levels of histamine.

hives—a raised, itchy area of skin that is usually a sign of an 

allergic reaction.

immune system—a complex network of cells, tissues, and 

organs that defends the body against attacks by disease-causing 

microbes.

immunoglobulin—one of a large family of proteins, also known 

as antibody.

lactase—the enzyme responsible for breaking down lactose in 

the gut. Lactase is produced by cells lining the small intestine.

lactose intolerance—the inability to digest lactose, a kind of 

sugar found in milk and other food products, because of a 

shortage of the enzyme lactase.
28NIAID I FOOD ALLERGY

mast cells—large granule-containing cells that are found in body 

tissues where typical allergic reactions occur.

microbes—tiny life forms, such as bacteria and fungi, that are 

visible only under a microscope. They may cause disease.

molecule—a group of atoms chemically joined together. In a 

cell, examples of different molecules include proteins, fats, and 

carbohydrates.

proteins—large molecules composed of one or more chains of 

amino acids.

tolerance (to food)—a state in which a person with a food allergy 

fails to develop allergic reactions after ingesting specific foods. 

This lack of response is sustained over a long period of time.

tissues—groups of cells that have a similar structure and work

together to perform a specific function.

toxins—agents produced by plants and bacteria that are 

poisonous and may also trigger allergic reactions.
29 NIAID I Food Allergy

More Information
 

general Information 

National Institute of Allergy and Infectious Diseases 

National Institutes of Health 

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Bethesda, MD 20892–6612 

866–284–4107 or 301–496–5717 

www.niaid.nih.gov

National Library of Medicine 

MedlinePlus 

8600 Rockville Pike 

Bethesda, MD 20894 

888–FIND–NLM (888–346–3656) or 301–594–5983 

www.medlineplus.gov

Allergy & Asthma Network Mothers of Asthmatics 

8201 Greensboro Drive, Suite 200 

McLean, VA 22102 

800–878–4403 

www.aanma.org

American Academy of Allergy, Asthma & Immunology 

555 East Wells Street, Suite 1100 

Milwaukee, WI 53202–3823 

414–272–6071 

www.aaaai.org

American Academy of Pediatrics 

141 Northwest Point Boulevard 

Elk Grove Village, IL 60007–1098 

800–433–9016 or 847–434–4000 

www.aap.org
30NIAID I FOOD ALLERGY

American College of Allergy, Asthma & Immunology

85 West Algonquin Road, Suite 550

Arlington Heights, IL 60005

847–417–1200

www.acaai.org

Asthma and Allergy Foundation of America

8201 Corporate Drive, Suite 1000

Landover, MD 20785

800–7–ASTHMA (800–727–8462) or 202–466–7643

www.aafa.org

Food Allergy and Anaphylaxis Network

11781 Lee Jackson Highway, Suite 160

Fairfax, VA 22033–3309

800–929–4040

www.foodallergy.org

Food Allergy Initiative

515 Madison Avenue, Suite 1912

New York, NY 10022–5403

855–FAI–9604 (855–324–9604)

www.faiusa.org

Allergy Extracts

Food and Drug Administration

Center for Biologics Evaluation and Research

10903 New Hampshire Avenue

Silver Spring, MD 20993–0002

888–INFO–FDA (888–463–6332)

www.fda.gov/cber
31NIAID I FOOD ALLERGY

Celiac Disease and Lactose Intolerance

National Institute of Diabetes and Digestive 

and Kidney Diseases

National Digestive Diseases Information Clearinghouse

National Institutes of Health

1 Information Way

Bethesda, MD 20892–3570

800–860–8747

www.digestive.niddk.nih.gov

Eczema

National Arthritis and Musculoskeletal and Skin Diseases 

Information Clearinghouse

National Institutes of Health

1 AMS Circle

Bethesda, MD 20892–3675

877–22–NIAMS (877–226–4267) or 301–495–4484 

www.niams.nih.gov

American Academy of Dermatology

P.O. Box 4014

Schaumburg, IL 60168–4014

866–503–SKIN (866–503–7546) or 847–247–1280

www.aad.org

National Eczema Association for Science and Education

4460 Redwood Highway, Suite 16D

San Rafael, CA 94903–1953

800–818–7546 or 415–499–3474

www.nationaleczema.org
32NIAID I FOOD ALLERGY

Food Contents

U.S. Department of Agriculture

Food and Nutrition Information Center

National Agricultural Library

10301 Baltimore Avenue, Room 105

Beltsville, MD 20705

301–504–5414

www.nal.usda.gov/fnic

Food Facts

American Dietetic Association

120 South Riverside Plaza, Suite 2000

Chicago, IL 60606–6995

800–877–1600 or 312–899–0040

www.eatright.org/public
33NIAID I FOOD ALLERGY

Credits

Cover © Getty Images

Facing Contents © iStockphoto

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Page 10 (top to bottom) © iStockphoto

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Page 17 © iStockphoto

Page 18 © iStockphoto

Page 19 NIAID

Page 20 © iStockphoto

Page 22 © Getty Images

Page 23 © iStockphoto

Page 25 © iStockphoto


U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

National Institutes of Health

National Institute of Allergy 

and Infectious Diseases

NIH Publication No. 12-5518 

July 2012

www.niaid.nih.gov