ﾗﾘｰﾈﾙﾋﾞﾙﾊﾞｵｱﾊﾞｵ December 4, 2009
Masters Program in Animal Hygiene and Food Safety うらしま先生
Food Allergy Lecture
Ever since I was a child, I was fascinated (and sometimes felt pity) with people who have
food allergies. Some of the food allergies from the people that I have met in my life
ranged from milk to sea foods. In the case of sea foods, my friends develop rashes. I
always try to wonder what prevents them from enjoying food just like ordinary people.
Because of this, I realized that I need to thank God for so many things because I do not
have food allergies (which will prevent me from enjoying foods to the fullest).
That is why I really appreciated the Food Hygiene lecture on Food Allergy of Dr. Keiko
Kawamoto November 30, 2009. She talked about food allergens, the Big Eight (8) of
food allergy, and how to manage food allergy. According to Wikipedia, a food allergy is
an adverse immune response to a food protein. Food allergy is distinct from other
adverse responses to food, such as food intolerance, pharmacologic reactions, and
toxin-mediated reactions. Please see Table 1 for the Food Allergy Description.
Table 1. Food Allergy Description
Food Allergy Pharmacologic Toxins Intolerance
Adverse immune Caffeine tremors, Bacterial food Lactose intolerance
response to a food cheese/wine poisoning, (lactase deficiency
protein (tyramine) migraine, staphylotoxin
scombroid
(histamine) fish
poisoning
The food protein triggering the allergic response is termed a food allergen. It is
estimated that up to twelve (12) million Americans have food allergies,1 and the
prevalence is rising. Six (6) to eight (8) percent of children under the age of three have
food allergies and nearly four (4) percent of adults have them.2 Food allergies cause
roughly 30,000 emergency room visits and one hundred (100) to two hundred (200)
deaths per year in the United States. The most common food allergies in adults are
shellfish, peanuts, tree nuts, fish, and eggs, and the most common food allergies in
children are milk, eggs, peanuts, and tree nuts. As noted by Dr. Kawamoto, food
allergies are mostly inherent in children. She further noted that that there is an
increasing prevalence of food allergies in Japan with about ten (10) to fifteen (15)
percent of the population having experienced it.
1
"Food Allergy Media Q&A" (PDF). Food Allergy & Anaphylaxis Network.
http://www.foodallergy.org/media/MediaQA.pdf. Retrieved 2008-01-26.
2
National Institute of Allergy and Infectious Diseases (July 2004). "Food Allergy: An Overview" (PDF). National
Institutes of Health. pp. 35. http://www.niaid.nih.gov/publications/pdf/foodallergy.pdf.
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Signs and symptoms. Classic immunoglobulin-E (IgE)-mediated food allergies are
classified as type-I immediate hypersensitivity reactions. These allergic reactions have
an acute onset (from seconds to one hour) and may include:
• Angioedema: soft tissue swelling, usually involving the eyelids, face, lips, and
tongue. Angioedema may result in severe swelling of the tongue as well as the
larynx (voice box) and trachea, resulting in upper airway obstruction and difficulty
breathing;
• Hives;
• Itching of the mouth, throat, eyes, skin;
• Nausea, vomiting, diarrhea, stomach cramps, and/or abdominal pain. This group
of symptoms is termed gastrointestinal hypersensitivity;
• Rhinorrhea, nasal congestion;
• Wheezing, scratchy throat, shortness of breath, or difficulty swallowing; and
• Anaphylaxis: a severe, whole-body allergic reaction that can result in death.
Food allergy is thought to develop more easily in patients with the atopic syndrome, a
very common combination of diseases: allergic rhinitis and conjunctivitis, eczema and
asthma.3 The syndrome has a strong inherited component; a family history of allergic
diseases can be indicative of the atopic syndrome. Conditions caused by food allergies
are classified into 3 groups according to the mechanism of the allergic response: (1) IgE-
mediated (classic); (2) IgE and/or non-IgE-mediated; and (3) Non-IgE mediated.
The big eight (8). The most common food allergies are from:4 dairy , eggs, peanut ,
tree nut, sea foods, shellfish, soy, and wheat. These are often referred to as "the big
eight (8)," because they account for over ninety (90) percent of the food allergies in the
United States. The top allergens vary somewhat from country to country but milk, eggs,
peanuts, tree nuts; fish, shellfish, soy, wheat and sesame tend to be in the top ten (10) in
many countries. Allergies to seeds - especially sesame - seem to be increasing in many
countries.
Diagnosis. The best method for diagnosing a food allergy is to be assessed by an
allergist. The allergist will review the patient's history and the symptoms or reactions
that have been noted after food ingestion. If the allergist feels the symptoms or
reactions are consistent with the food allergy, he will perform allergy tests.
Examples of allergy testing include:
• Skin prick testing is easy to do and results are available in minutes. Different
allergists may use different devices for skin prick testing. Some use a "bifurcated
needle", which looks like a fork with two (2) prongs. Others use a "multi-test",
which may look like a small board with several pins sticking out of it. In these
tests, a tiny amount of the suspected allergen is put onto the skin or into a testing
device, and the device is placed on the skin to prick, or break through, the top
layer of skin. This puts a small amount of the allergen under the skin. A hive will
form at any spot where the person is allergic. This test generally yields a positive
3
"Other atopic dermatitis and related conditions". ICD9.
http://www.icd9data.com/2007/Volume1/680-709/690-698/691/691.8.htm.
4
"Food Allergy Facts & Figures". Asthma and Allergy Foundation of America. March 28, 2007.
http://www.aafa.org/display.cfm?id=9&sub=30.
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or negative result. It is good for quickly learning if a person is allergic to a
particular food or not, because it detects allergic antibodies known as IgE. Skin
tests cannot predict if a reaction would occur or what kind of reaction might occur
if a person ingests that particular allergen. They can however confirm an allergy
in light of a patient's history of reactions to a particular food. Non-IgE mediated
allergies cannot be detected by this method.
• Blood tests are another useful diagnostic tool for evaluating IgE-mediated food
allergies. For example, the RAST (RadioAllergoSorbent Test) detects the
presence of IgE antibodies to a particular allergen. A CAP-RAST test is a
specific type of RAST test with greater specificity: it can show the amount of IgE
present to each allergen.5 Researchers have been able to determine "predictive
values" for certain foods. These predictive values can be compared to the RAST
blood test results. If a persons RAST score is higher than the predictive value for
that food, then there is over a 95% chance the person will have an allergic
reaction (limited to rash and anaphylaxis reactions) if they ingest that food.
Currently, predictive values are available for the following foods: milk, egg,
peanut, fish, soy, and wheat.6 Blood tests allow for hundreds of allergens to be
screened from a single sample, and cover food allergies as well as inhalants.
However, non-IgE mediated allergies cannot be detected by this method.
• Food challenges, especially double-blind placebo-controlled food challenges
(DBPCFC), are the gold standard for diagnosis of food allergies, including most
non-IgE mediated reactions. Blind food challenges involve packaging the
suspected allergen into a capsule, giving it to the patient, and observing the
patient for signs or symptoms of an allergic reaction. Due to the risk of
anaphylaxis, food challenges are usually conducted in a hospital environment in
the presence of a doctor.
• Additional diagnostic tools for evaluation of eosinophilic or non-IgE mediated
reactions include endoscopy, colonoscopy, and biopsy.
Treatment. The mainstay of treatment for food allergy is avoidance of the foods that
have been identified as allergens. For people who are extremely sensitive, this may
involve the total avoidance of any exposure with the allergen, including touching or
inhaling the problematic food as well as touching any surfaces that may have come into
contact with it.
Future directions. Food and health experts expect that vaccines can in theory be
created using genetic engineering to cure allergies. If this can be done, food allergies
could be eradicated in about ten (10) years. In conclusion, much research work lies
ahead in the field of food allergy since there is still no known cure for this kind of
problem. Future researches should be geared towards finding the cure to solve food
allergy problems.
5
"What is a RAST test ? What is a CAP-RAST test?". kidswithfoodallergies.org.
6
Sampson, HA; Ho DG (October 1997). "Relationship between food-specific IgE concentrations and the risk of positive
food challenges in children and adolescents". J Allergy Clin Immunol 100 (4): 444–51.
doi:10.1016/S0091-6749(97)70133-7. PMID 9338535.
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