Food Allergies

Up to 2 million, or 8%, of children, and 2% of adults in the United States are estimated to have food allergies.

With food allergy, an individual’s immune system will overreact to an ordinarily harmless food. This is caused by an allergic antibody called IgE (Immunoglobulin E), which is found in people with allergies. This antibody may develop after eating the food repeatedly in the past but without having problems. Food allergy may appear more often in someone who has family members with allergies, and symptoms may occur after that allergic individual consumes even a tiny amount of the food.

Food intolerance is sometimes confused with food allergy. Food intolerance refers to an abnormal response to a food or food additive that is not an allergic reaction. It differs from an allergy in that it does not involve the immune system. For instance, an individual may have uncomfortable abdominal symptoms after consuming milk. This reaction is most likely caused by a milk sugar (lactose) intolerance, in which the individual lacks the enzymes to break down milk sugar for proper digestion.

Food allergens -those parts of foods that cause allergic reactions-are usually proteins. Most of these allergens can still cause reactions even after they are cooked or have undergone digestion in the intestines. Numerous food proteins have been studied to establish allergen content. Some allergens (most often from fruit and vegetables) cause allergic reactions only if eaten before being cooked. Most such reactions are limited to the mouth and throat.

The most common food allergens are the proteins in cow’s milk, eggs, peanuts, wheat, soy, fish, shellfish and tree nuts.

All foods come from either a plant or an animal source, and foods are grouped into families according to their origin. In some food groups, especially tree nuts and seafood, an allergy to one member of a food family may result in the person being allergic to all the members of the same group. This is known as cross-reactivity. However, some people may be allergic to both peanuts and walnuts, which are from different food families; these allergies are called coincidental allergies, because they are not related.

Within animal groups of foods, cross-reactivity is not as common. For example, people allergic to cow’s milk can usually eat beef, and those allergic to eggs can usually eat chicken.

With shellfish, crustaceans (shrimp, crab and lobster) are most likely to cause an allergic reaction. Molluscan shellfish (clam, oysters, abalone, etc.) can be allergenic, but reactions to these shellfish are less common. Occasionally, people are allergic to both types of shellfish.

Symptoms of allergic reactions to foods

The most common allergic skin reaction to a food is hives. Hives are red, very itchy, swollen areas of the skin that may arise suddenly and leave quickly. They often appear in clusters, with new clusters appearing as other areas clear. Hives may occur alone or with other symptoms.

Atopic dermatitis, or eczema, a skin condition characterized by itchy, scaly, red skin, is commonly triggered by food allergy. This reaction is often chronic, occurring in individuals with personal or family histories of allergies or asthma.

Asthma symptoms such as coughing, wheezing, or difficulty breathing due to narrowed airways, may be triggered by food allergy, especially in infants and children.

Gastrointestinal symptoms of food allergy include vomiting, diarrhea and abdominal cramping, and sometimes a red rash around the mouth, itching and swelling of the mouth and throat, abdominal pain, swelling of the stomach and gas.

In infants, non-allergic, temporary reactions to certain foods, especially fruits, are common. For example, a rash around the mouth, due to natural acids in foods like tomatoes and oranges, or diarrhea due to excess sugar in fruit juice or other beverages, occur with some frequency. However, other reactions are allergic and may be caused by traces of the offending food when eaten again. As they grow older, some children may tolerate foods that previously caused allergic reactions.

Most children with egg, milk, wheat and soy allergies will outgrow these with time.  Approximately 10-20% of children with peanut and tree nut allergies will outgrow this one however.  Periodic food allergy check-ups with appropriate food challenges should be carried out under the supervision of an allergist.

Severe allergic reactions

In severe cases, consuming a food to which one is allergic can cause a life-threatening reaction called anaphylaxis- a systemic allergic reaction that can be severe and sometimes fatal. The first signs of anaphylaxis may be a feeling of warmth, flushing, tingling in the mouth or a red, itchy rash. Other symptoms may include feelings of light-headedness, shortness of breath, severe sneezing, anxiety, stomach cramps and/or vomiting and diarrhea. In severe cases, some people may experience a drop in blood pressure that results in a loss of consciousness and shock. Without immediate treatment, anaphylaxis may cause death.

Symptoms of anaphylaxis are reversed by treatment with injectable epinephrine (EpiPen or TwinJect) and other emergency measures. It is essential that anyone with symptoms suggesting possible anaphylaxis get emergency treatment immediately.


Diagnosis of food allergy requires a carefully organized and detailed assessment of the problem. Allergy skin tests may be helpful to determine which foods, if any, are triggering your or your child’s allergic symptoms. In skin testing, a small amount of liquid extract made from the food is placed on the back or arm. In a test called a prick test, a needle is then passed through the liquid on the top layer of the skin. In some cases fresh foods may be needed for skin testing.

If you or your child develops a wheal-a raised bump or small hive-within 20 minutes, this positive response indicates a possible allergy. If a wheal does not develop, the test is negative. It is uncommon for someone with a negative skin test to have an IgE-mediated food allergy. Skin tests are not helpful when sensitivity to chemical food additives is suspected.

Your doctor may also use blood tests for IgE to specific foods, called RAST testing or CAP-RAST, to diagnose food allergies. In certain cases, such as severe eczema all over the body, an allergy skin test cannot be done. Your doctor may recommend a food RAST blood test to obtain similar information to that found with a skin test. For diagnosis of milk, egg, peanut or fish allergy, the level of the CAP-RAST test may help predict future food allergy reactions to these foods. False positive results may occur with both food allergy skin testing and blood testing.

If the diagnosis of food allergy remains in doubt, your allergist may recommend a food challenge test. These tests are conducted in the doctor’s office.

An excellent resource and support group for those with food allergy is the Food Allergy and Anaphylaxis Network (FAAN): 1-800-929-4040 or  There are also some well-written books about the subject of food allergy including:

  • On the Nature of Food Allergy by Paul Hannaway, MD
  • The Peanut Allergy Answer Book by Michael Young, MD


Avoid the food. The best way to treat food allergy is to avoid the specific foods that trigger the allergy.

Ask about ingredients.

  • To avoid eating a “hidden” food allergen away from home, food-allergic individuals must always inquire about ingredients when eating at restaurants or others’ homes and make the seriousness of their allergy known.
  • Although it has been shown that just smelling peanut butter will not cause a reaction, sometimes food allergens can be airborne, especially in steam, and can cause reactions. Boiling or simmering seafoods have been particularly implicated.

Read food labels. It is important for food-allergic people to carefully read food labels.  Some foods may be listed by the name of their proteins.  For example:

  • Milk: casein, lactalbumin, lactoglobulin
  • Egg: albumin
  • Peanut: cold-pressed oil contains peanut protein; ‘highly-refined’ does not
  • Tree nuts: almond, brazil nut, cashew, hazelnut, filbert, pecan, pinon, pistachio, walnut
  • Soy: tofu, soy protein; NOTE soy lecithin is okay to eat

Be prepared for emergencies. Anaphylactic reactions caused by food allergies can be potentially life-threatening. Those who have experienced an anaphylactic reaction to a food must strictly avoid that food. They need to carry and know how to use injectable epinephrine and antihistamines to treat reactions due to accidental ingestion.

You should always carry at least two doses of epinephrine and make sure that the EpiPen or AuviQ is kept with you and not in the car or other location. People who are commonly around you or your child, such as spouses, parents, co-workers, school nurses, teachers or daycare workers, should also know how to use the injectable epinephrine.

Those with food allergies should also wear an identification bracelet that describes the allergy.

If you have an anaphylactic reaction after eating a food, it is essential that you have someone take you to the emergency room, even if symptoms subside. For proper diagnosis and treatment, make sure to get follow-up care from your allergist.

When should an epinephrine injection be given to a patient with a known food allergy who has ingested the food in question, but has no symptoms


One question that plagues us as the “Food Allergy Action Plan” season is upon us…what is the official recommendation regarding use of epinephrine in patients with a known food allergy who have ingested the allergenic food but have no symptoms? Many practitioners in our area instruct patients that if there are no symptoms, the patient should receive diphenhydramine and be monitored closely. However, a teenager died in our area recently after eating a peanut, and she initially had no symptoms so was given diphenhydramine and was observed as they had been instructed by their doctors. She then began to vomit 20 minutes later and died of laryngeal edema despite 3 rounds of injectable epinephrine.


There is no “official recommendation” regarding the issue you present. There is no consensus of opinion in this regard, and different physicians utilize different strategies.

You have asked a question which has prompted many debates over the years. We are not going to be able to settle this debate definitively in my response to you. However, I will give you my opinion and hopefully enlighten you on the issues underlying this debate and sharpen your appreciation for it.

First of all, your question is extremely timely in view of a recent death from anaphylaxis in a 14 year-old girl. I think you would appreciate the stance of the physicians in your community who have given you instructions regarding the administration of epinephrine to a greater extent if you will take the time to go to the link (ABC News) copied below. From that link you will also hear stories of other fatalities due to anaphylaxis related to the inadvertent ingestion of a food to which the individual was sensitive. These cases illustrate a very important point. That is, the mean time to respiratory or cardiovascular arrest after the ingestion of a food to which a patient is allergic is 30 minutes (Pumphrey RS, Clinical and Experimental Allergy 2000; 30(8):1144-1150). Thus there is very little time for one to act after patients express even the mildest symptom of an anaphylactic event.

Nonetheless, we have all seen children (and adults) who experience initial symptoms such as itching of the back of the throat or nausea after eating a food, and who recover spontaneously. In the practice of Allergy, we do food allergen challenges on a regular basis and observe these spontaneous recoveries. Thus we are all prejudiced by these observations. These personal anecdotal observations have resulted in the debate as framed in this quote from the Journal of allergy and Clinical Immunology:

“Although there is little debate about using epinephrine to treat a SCIT SR” (meaning anaphylactic reactions to injection of an allergen), “there is a lack of consensus about when it should be first used.”

This debate has certainly extended to anaphylactic reactions to foods. The issue is not whether epinephrine is the drug of choice. Clearly it is. Other agents such as antihistamines do not act in time to prevent fatalities. Thus if we are going to prevent a fatality, the only tool we have to do so is epinephrine.

The question then becomes an analysis of risk/benefit ratio. That is, what is the risk of giving epinephrine versus the potential benefit. I have copied below quotes dealing with this issue from the Guidelines for the treatment of Anaphylaxis published by the Washington State School District as well as the medical literature.

“Based on available evidence, the benefit of using appropriate doses of intramuscular epinephrine in

anaphylaxis far exceeds the risk…. Consensus opinion and anecdotal evidence recommend epinephrine administration sooner rather than later, that is, when the initial signs and symptoms of anaphylaxis occur, regardless of their severity, because fatalities in anaphylaxis usually result from delayed or inadequate administration of epinephrine.”

Furthermore, from the same source it states: “If a student, known to have anaphylaxis, has an exposure or a suspected exposure to an allergen, epinephrine is to be given immediately and the EMS (911) system activated.”

This same source, which I think is an excellent review of the issues you posed with your inquiry, recognizes that this puts a difficult decision-making process upon the shoulders of those administering epinephrine to a child in the school system. It states: “There is a natural reluctance to wait to administer epinephrine until symptoms worsen and you are sure the student is experiencing an anaphylactic reaction. There is the same reluctance to call 911. Many fatalities occur because the epinephrine was not administered in a timely manner.”

Thus, the doubts that you are having are actually universal, and I clearly understand them. However, reviewing all of the quotes above (and others copied for you below) and all of our available evidence, it would be my opinion the instructions you have been given are correct, and I have no problem with them whatsoever. It is quite clear that the potential side effects of administration of epinephrine to a child in the appropriate dose by intramuscular injection are not serious, and comparing these side effects to the potential of saving a life in my opinion favors the administration of epinephrine in the situation that you describe.

Having said this, as I mentioned at the beginning of my response, this answer cannot be dogmatic, and it is certainly recognized that there are differences of opinion amongst experts in this regard. So, in the final analysis, since it would be impossible for us to do a study to compare the two strategies (delayed versus immediate administration), one is left with isolated case reports, personal experience, and one’s own philosophy as to how to act in such a situation as you described.

As you can see from my response, I favor the aggressive approach, and feel that this is the safest strategy for you to employ in the setting in which you work.

The quotes and links copied below below further support support this opinion and are added if you would like to read more references related to you inquiry.

Anaphylaxis is a potentially life-threatening condition, requiring immediate medical attention. Most fatalities occur due to delay and delivery of the needed medication. Although many medications may be used for treating anaphylaxis, epinephrine is the life-saving medication that must be given immediately to avoid death.

“Practicing implementation of the ECP can be the most effective strategy to overcome the tendency to delay and to decrease the likelihood of a student fatality.”

“Epinephrine has long been regarded as the treatment of choice for acute anaphylaxis. This is true despite the recognition of its potential hazards. Alternative treatments – such as antihistamines, sublingual isoproterenol, inhaled epinephrine, and corticosteroids without epinephrine – have failed to prevent or relieve severe anaphylactic reactions. It is therefore inappropriate to use them for the first-line treatment or prevention of anaphylaxis.”

“Experts may differ on how they define the clinical threshold by which they define and treat anaphylaxis. However, they have no disagreement whatsoever that appropriate doses of intramuscular epinephrine should be administered rapidly once that threshold is reached. There is no absolute contraindication to epinephrine administration in anaphylaxis, and all subsequent therapeutic interventions depend on the initial response to epinephrine”.

In July 2008, the World Allergy Organization published the following statements:

“Anaphylaxis is an acute and potentially lethal multisystem allergic reaction. Most consensus guidelines for the past 30 years have held that epinephrine is the drug of choice and the first drug that should be administered in acute anaphylaxis. Some state that properly administered epinephrine has no absolute contraindication in this clinical setting. A committee of anaphylaxis experts assembled by the World Allergy Organization has examined the evidence from the medical literature concerning the appropriate use of epinephrine for anaphylaxis. The committee strongly believes that epinephrine is currently underused and often dosed suboptimally to treat anaphylaxis, is underprescribed for potential future self-administration, that most of the reasons proposed to withhold its clinical use are flawed, and that the therapeutic benefits of epinephrine exceed the risk when given in appropriate intramuscular doses.”

AAAAI Board of Directors, “Position Statement Anaphylaxis in Schools and Other Child-Care Settings,” 2008,

The Journal of Allergy and Clinical Immunology

Volume 125, Issue 3 , Pages 569-574.e7, March 2010

“Although there is little debate about using epinephrine to treat a SCIT SR, there is a lack of consensus about when it should be first used”


Phil Lieberman, M.D.


This is a handout from the Asthma and Allergy Affiliates reviewing current data and understanding of the management of food allergy.  These handouts are intended for our patients and are not a substitute for discussing your (or your child’s) unique situation with one of our physicians.