FOOD ALLERGY: Causes, Symptoms and Prevention

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.