What Are the Most Common Food Allergies?

Patient Presentation
A 14-year-old female came to the emergency room because of increasing respiratory distress.
She was known to be allergic to peanuts and other tree nuts and had moderate, persistent asthma.
She was visiting relatives and the entire family had gone hiking and picked up butternuts and walnuts.
She did not pick up or touch any of the nuts, but did ride home in a station wagon where some of the nuts were transported in the back end of the car.
During the ride, she became nauseated. The family stopped for a while and she seemed to be better. However, when the car ride resumed so did the nausea.
When they reached home she was wheezing. Her rescue inhaler did not help and her parents took her to the emergency room. She did not use her injectable epinephrine.
The past medical history showed peanuts and tree nuts triggering significant asthma flares and severe pruritus. She had never had laryngospasm or needed intubation.
The most recent episode had been 2 years previous when she had ingested some frozen yogurt that initially had a cookie in it.
She did not eat the cookie, but it was suspected that the cookie’s oil was peanut or tree nut and had permeated the yogurt.
The family history showed mild asthma and eczema.
The review of systems was otherwise normal.
The pertinent physical exam showed a wide-eyed young female who could speak with difficulty but was alert and oriented. Her heart rate was 148 beats/minute, respiratory rate was 64 respirations/minute, her blood pressure was 108/70 and her saturation was 90% on room air.
Her skin examination revealed diffuse hives. HEENT was normal. She had increased work of breathing with intercostal retractions and tracheal tugging. She had diffuse wheezing throughout her lung examination.
The diagnosis of a severe allergic reaction was made.
She and her family realized that either she inadvertently contacted the nuts, or that the oils from the nuts were aerosolized within the car triggering her symptoms.
In the emergency room, the patient’s clinical course improved somewhat with subcutaneous epinephrine, oral diphenhydramine and oral prednisone.
She, her parents and the emergency room staff felt she should be monitored and so she was admitted overnight and then discharged home.

Food allergies are relatively common but it can be difficult to tease out if it is a true allergy, a food intolerance or is actually something else.
Risk factors that increase the likelihood of food allergy include:

  • Reactions that occur minutes to hours of the ingestion
  • Accidental ingestion of same food that produces the same symptoms
  • Onset of symptoms as an infant or young child
  • Close family history of other allergic diseases such as allergic rhinitis, asthma, atopic dermatitis or food allergies
  • The suspected food is known to be higher risk for producing allergic reactions

Children with a possible food allergy may receive testing by skin-prick, patch testing or RAST (radioallergosorbent testing).
RAST is a blood test that has a high sensitivity but has only ~50% specificity. It is commonly performed in young children because it is often easier to obtain blood than to do skin-prick or patch testing. It also does not carry a risk of inducing potential allergic reactions.

Children with a history of anaphylaxis should be treated as if they have severe food allergies and should be evaluated and treated by a specialist.
Children with a history of symptoms after ingestion of a food, but no anaphylaxis and with positive testing may need further testing with a blinded or unblinded food challenge.
Children with a history of symptoms after ingestion of a food, but no anaphylaxis and negative testing often can be allowed the food and monitored. But if there is a family history of anaphylaxis the patient should be evaluated by a specialist and most likely will have the food re-introduced in a supervised setting.

If in doubt about if the child is allergic, they should be treated as if they are.
Patients should be given injectable epinephrine and have it available at all times. This may mean that they need several injectors to be available at school, home, other locations the patient frequents and also available in backpacks/purses, etc. if the child is old enough to use the injector themselves.
Patients and parents need to be told that if the epinephrine is given then they must go to the nearest hospital as soon as possible for evaluation. Second injectors are also sometimes recommended as the epinephrine wears off in about 20 minutes and this may not be enough time for the patient to have gotten to the hospital yet. The second epinephrine injection can therefore be given enroute.

Parents should be educated to CONSTANTLY read all labels and ask about food preparation at restaurants, schools and other non-home locations.
Label reading is extremely important as ingredients and preparation may have changed from the last time the food was ingested.
Generic and brand name products may be prepared differently so every label must be checked.
Patients and parents should be educated that if they are in doubt about a food, the entire food and anything it came in contact with should be avoided (see the yogurt incident above).

Peanut allergies are highly genetic with a child have 7 times greater risk of being allergic if his/her parent or sibling has a peanut allergy. In monozygotic twins there is a 64% likelihood of peanut allergy if the other twin has the problem.
Genetics does not account for all of the reasons for food allergy and it may be multi-factorial. There are several hypotheses for food allergies which include dual-allergens, antioxidants, dietary fat, vitamin D, and general hygiene.

Learning Point
The prevalence of food allergies depends on the definition and location internationally. Some are regional allergies such as mustard allergy in France or royal jelly allergy in Hong Kong.
A recent metaanalysis of international studies showed there is a large difference between self-reported and challenge-proven prevalence.

Prevelence of food allergies. All numbers are percentages.

Food		Self reported	Challenge-proven
Milk		1.2-17		0-3
Egg		0.2-7		0-1.7
Peanut		0-2		0.2-1.6
Any food 	3-35		1-10.8

Overall, egg and milk are the most common food allergies.
In children, egg, milk, soy, wheat and peanut allergies predominate.
In adults, crustaceans, tree nuts, peanuts and fish predominate.

Questions for Further Discussion
1. How can children with severe food allergies be accommodated in the lunch room at school?
2. How can airplane flights be made safer for patients with severe food allergies?
3. Up to what age can exclusive breast feeding prevent or delay atopic dermatitis, cow milk allergy and wheezing?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Allergy and Food Allergy and at Pediatric Common Questions, Quick Answers for this topic: Milk Allergy


To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

Rona RJ, Keil T, Summers C, Gislason D, Zuidmeer L, Sodergren E, Sigurdardottir ST, Lindner T, Goldhahn K, Dahlstrom J, McBride D, Madsen C.

The prevalence of food allergy: a meta-analysis.
J Allergy Clin Immunol. 2007 Sep;120(3):638-46.

Kurowski K, Boxer RW.
Food allergies: detection and management.
Am Fam Physician. 2008 Jun 15;77(12):1678-86.

Lack G.
Epidemiologic risks for food allergy.
J Allergy Clin Immunol. 2008 Jun;121(6):1331-6.

Zuidmeer L, Goldhahn K, Rona RJ, Gislason D, Madsen C, Summers C, Sodergren E, Dahlstrom J, Lindner T, Sigurdardottir ST, McBride D, Keil T.
The prevalence of plant food allergies: a systematic review.
J Allergy Clin Immunol. 2008 May;121(5):1210-1218.e4.

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    4. Patient management plans are developed and carried out.
    5. Patients and their families are counseled and educated.
    7. All medical and invasive procedures considered essential for the area of practice are competently performed.
    8. Health care services aimed at preventing health problems or maintaining health are provided.
    9. Patient-focused care is provided by working with health care professionals, including those from other disciplines.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Interpersonal and Communication Skills
    17. A therapeutic and ethically sound relationship with patients is created and sustained.
    18. Using effective nonverbal, explanatory, questioning, and writing skills, the healthcare professional uses effective listening skills and elicits and provides information.
    19. The health professional works effectively with others as a member or leader of a health care team or other professional group.

  • Systems Based Practice

    26. Partnering with health care managers and health care providers to assess, coordinate, and improve health care and how these activities can affect system performance are known.

    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital

    October 20, 2008