Food Allergy
An adverse food reaction consists of any abnormal reaction after
the ingestion of a food. It may be due to a food intolerance, which is an
adverse physiologic response, or to food hypersensitivity (allergy), which is
an adverse immunologic reaction (Hugh, 2003). Food allergy is
a potentially serious immune response to eating specific foods or food
additives (Branum, 2008). The
term food allergy is used when an immunological mechanism has been defined or
is suspected (Cassim, 2004). Food allergy occurs in 6-8% of children and 2% of
adults (NIAID, 2003). More
than 160 foods can cause allergic reactions in people with food allergies; the
law identifies the eight most common allergenic foods. These foods account for
90% of food allergic reactions, and are the food sources from which many other
ingredients are derived (FDA, 2010). They also account for over 905 of allergic
reactions in affected individuals: milk,
eggs, peanuts, tree nuts, fish, shellfish, soy and wheat. Reactions to
these foods by an allergic person can range from a tingling sensation around
the mouth and lips and hives to death, depending on the severity of the
allergy. Food allergy is more prevalent
in children than adults, and the majority of affected children will outgrow
food allergies with age (Branum, 2008)
Underlying Mechanisms of Food Allergy
The
gastrointestinal tract processes ingested food for absorption. It neutralizes
foreign antigens and blocks them from entering the circulation. Enzymes from salivary,
gastric, pancreatic and intestinal secretions, combined with mastication,
gastric acid, and peristalsis, reduce ingested substances to small sugars,
peptides and fats. Non-specific (mucin coat) and specific (secretory IgA)
mechanisms ‘hold up' and/or block potentially harmful antigenic substances from
penetrating the intestinal barrier. Many of the immunological and mechanical
barriers involved in this process are immature at birth, leaving the infant at
risk. Large amounts of immunologically intact food proteins penetrate the gut
barrier in children and adults and enter into the circulation, but clinical
tolerance prevents pathologic reactions. A failure to develop tolerance or a
breakdown in tolerance results in excessive production of food-specific IgE
antibodies.
Mast
cells line the GI tract from the lips to the rectum. Food antigens are most
rapidly absorbed from the small intestine, colon and rectum and more slowly
from the oesophagus and stomach. When food allergens penetrate mucosal barriers
and reach specific IgE antibodies bound to mast cells, mediators such as
histamine, leukotrienes and prostaglandins are released inducing an immediate
hypersensitivity reaction manifested by vasodilatation, smooth muscle
contraction and other alterations in normal physiology (Cassim, 2004).
Risk
factors and symptoms
According to NIAID (2003) the risk
factors linked to food allergy include are: Family history of allergy and asthma, genetic predisposition to allergic disease, age (< 3 years old), elevated allergen-specific serum IgE concentration. According to
FDA (2010), the symptoms of food allergies typically appear from within a few minutes to two hours after a
person has eaten the food to which he or she is allergic. Allergic reactions vary in intensity and time of onset between individuals and may include:
- Hives, flushed skin or rash, tingling or
itchy sensation in the mouth
- Face, tongue or lip swelling
- Vomiting and or/diarrhea
- Abdominal cramps coughing or wheezing
- Dizziness and or light headaches
- Swelling of the throat and vocal cords
- Difficulty breathing
- Loss of consciousness
Persons
may still be allergic to- and have serious reactions to- foods other than the
eight foods identified by the law. So, always be sure to read the food label’s
ingredient list carefully to avoid food allergens in question.
What
to do if symptoms occur
The appearance of symptoms after eating
food may be a sign of a food allergy. The food that caused these symptoms
should be avoided, and the affected person, should contact a doctor or health
care provider for appropriate testing and evaluation.
Persons
with a known food allergy who begin experiencing symptoms while, or after,
eating a food should initiate treatment immediately, and go to a nearby
emergency room if symptoms progress.
Following
ingestion of a food allergen, a person with food allergies can experience a
severe, life threatening allergic reaction called anaphylaxis. This can lead
to:
- Constricted
air ways
- Severe
lowering of blood pressure and shock (“anaphylactic shock”)
- Suffocation
by swelling of the throat
Each
year in the U.S., it is estimated that anaphylaxis to food results in: 30,000
emergency room visits, 2000 hospitalizations and 150 deaths. Prompt administration of epinephrine by
autoinjector (e.g., Epi-pen) during early symptoms of anaphylaxis may help
prevent serious consequences.
Prevention
According
to Cassim (2004), the World Allergy Organization and the World Health Organization recommend exclusive breastfeeding only for the newborn
infant up to six months and no special diet for the lactating mother. Infants who
have cow milk allergy should avoid cow milk proteins, and if a supplement
is needed, hypoallergenic formula, if available, should be given to improve
symptom control. Individuals with food allergies should
alert restaurant personnel about their food allergy and ask whether ingredients
are contained in menu dishes or whether there is possible contamination of
foods due to shared preparation areas or equipment. Individuals allergic to egg should not
be given influenza vaccines without prior consultation with their physician.
According to the food and drug
administration (2004), persons found to have a food allergy
should be taught to read food labels and avoid the offending foods. They should also
be taught, in case of accidental ingestion, to recognize the early symptoms of
an allergic reaction, and be properly educated on- and armed with- appropriate
treatment measures.The food to which an individual is
allergic should be avoided. Where avoidance of the implicated food may result
in nutritional deficiency, dietary supplementation is necessary (FDA, 2010).
FDA’s
Role
To help Americans avoid the health risks posed by food allergens, congress
passed the food allergen labeling and consumer protection act of 2004 (FALCPA).
The law applies to all foods whose labeling is regulated by FDA, both and
imported (FDA regulates the labeling of all foods except for poultry, most
meats, certain egg products and mo0st alcoholic beverages.) Before
FALCPA, the labels of foods made from two or more ingredients were required to
list all ingredients by their common or usual names. The names of some
ingredients, however, do not clearly identify their food source.
Now,
the law requires that labels must clearly identify the food source names of all
ingredients that are- or contain any protein derived from- the eight most
common food allergens, which FALCPA defines as ‘major food allergens.” As
a result, food labels help allergic consumers to identify offending foods or
ingredients so they can more easily avoid them.
The FALCPA requires that food labels
identify the food source names of all major food allergens used to make the
food. This requirement is met if the common or usual name of an ingredient
(e.g., buttermilk) that is a major food allergen already identifies that
allergen’s food source name (i.e., milk). Otherwise, the allergen’s food source
name must be declared at least once on the food label in one of the two ways: In
Parentheses following the name of the ingredient, examples: Lecithin (Soy),
flour (wheat) and whey (milk) or immediately
after or next to the list of ingredients in a “contains” statement, example:
“contains wheat, milk and soy.”
References
Branum.A.M, Lukaca.S.L., 2008: Food allergy among
U.S. Children: Trends in Prevalence and hospitalizations. NCHS data Brief.
Cassim
M., 2004: Food Allergy
Food
and Drug administration, 2010
Hugh.A.S.,
2003: Food Allergy. Journal of allergy and clinical immunology 2003;111:S540-7
NIAID, National Institute of allergy and infectious
disease. Report of the expert panel on food allergy research, June 30 and
July,2003.
