Food Allergies, Food Intolerances and Food Aversion

Food Allergies

Food allergy is an adverse clinical reaction to food due to any type of abnormal immune response to food protein.
Food allergies can be broadly divided into those that are mediated by IgE (immunoglobulin E - a protein produced in lungs, skin and mucous membranes) and those that are not IgE-mediated. IgE-mediated allergies are usually acute in onset, e.g. anaphylaxis. Non-IgE mediated food allergies are sub-acute or chronic, and are mediated mainly by T cells.

The most common food allergens are cow's milk, egg, soy, wheat, peanuts, tree nuts, fish and shell fish.

Food allergy usually occurs in the first decade of life and is directly linked to the maturation of the immune system. In general, food allergy clinical symptoms are not detected at birth and, although the production of IgE starts in the eleventh week of gestation, no specific sensitization to food allergens can be detected in cord blood.
During the first months of life initial IgE responses to food proteins, particularly hen’s egg and cow's milk may be observed even in exclusively breast-fed infants. In such individuals, it is proposed that exposure occurs through proteins in their mother’s milk.
Fortunately, about 85% of children lose their adverse clinical reaction to allergenic foods in the first 3-5 years of life. However, persistence of childhood food allergy seems to be increasingly common.

It has been known for many years that atopic disease, a condition that can be related to food allergy, runs in families. “Atopy” identifies allergic diseases such as atopic dermatitis, bronchial asthma and hayfever, which tend to cluster in families and are associated with the production of specific IgE antibodies to common environmental allergens.
The risk of neonates having atopic symptoms during the first two decades of life strongly depends on the manifestation of the disease in their parents and siblings.
If one parent had an atopic disease then there was a 20% chance that the same disease would affect the child. If both parents had an atopic disease then this risk increased to over 40%. When both parents had an identical type of atopic disease the incidence of atopic disease was higher (72.2%) than when non-identical types occurred in the parents (20.8%). It has also been shown that maternal atopy poses a higher risk for infantile atopy than paternal atopy.

Many other risk factors for allergy have been identified, such as exposure to tobacco smoke during pregnancy, infancy and childhood; urban living; and indoor humidity or mould growth.

Food Intolerances

Food intolerance is a reproducible adverse reaction to the ingestion of food or to any of its components, i.e. proteins, carbohydrates, fats and additives. Such adverse reactions include metabolic reactions, enzyme deficiencies etc.

Food Aversion

Food aversion is psychological avoidance and psychological intolerance caused by emotions associated with food rather than the food itself.
Symptoms of food aversion do not appear when the food is given in an unrecognisable form.