Childhood is the period of life when allergies to food are most prevalent. Food allergy is much more common in babies and young children than in adults. Most food allergies are outgrown by the age of five years. Food allergy in adults is relatively uncommon. Estimates of food allergy in adults indicate an incidence of less than 2 %. However, food allergy intolerance of food components, naturally occurring chemicals, and food additives is a frequent experience, and some practitioners estimate the incidence of these conditions as high as 50 % of the adult population. Food allergy is a response of the immune system; a food intolerance can be broadly defined as a sensitivity mechanism that does not involve the immune system. Food intolerance is usually due to a physiological reaction such as an enzyme deficiency. We shall talk about the differences between food allergy and food intolerance later in this article.
Incidence of Food Allergies in Children
It is difficult to determine exactly how many babies and children are sensitive to foods and suffer symptoms as a result of eating or drinking. There is no single reliable laboratory test that can prove that children allergies or intolerant to a specific food or food additive. This makes estimating how frequently such reactions occur very difficult. Because there are so many different immunological response and non-immunological reactions involved in food sensitivity symptoms, it would be unrealistic to expect that a laboratory test alone could identify them all. In the end, the only accurate way to determine child allergies or reactivity to a food, drink, or food additive is elimination and challenge, and this process is too expensive and time-consuming to be a routine procedure.
However, based on the statistics that are available, it is usually estimated that food allergy occurs in up to 8 % of children under the age of five years, and that 2 % of children in this age group have an allergic reaction to cow’s milk proteins. Based on specific studies, 4 to 6 % of children had documented food allergy. The overall incidence of cow’s milk allergy in children ranged from 1.9 to 7.5 % in different populations. Other reports suggest the incidence of food allergy in children to be up to 8 % and “food-related complaints” to afflict as many as 28 % of children.
An Australian study indicated that at the age of 2 years, egg was the most frequent food allergen (3.2 %), while cow milk allergy (2.0 %) in children and peanut (1.9 %) were fairly equal in frequency. Allergy to wheat, soy, sesame seed, cashew nuts, hazelnuts, and walnuts was less frequent and about equal in prevalence. Allergies to fish, Brazil nuts, and shell fish were quite uncommon. In Asian countries the reported frequency was remarkably similar to that in Australia, except allergy to seafood was more common than for nuts, peanuts, and wheat, if seafoods were a regular part of the infant’s diet. Rice hypersensitivity was rare in Australia and in Asian countries.
Progress of Food Allergies in Children
Early infancy is a particularly critical time because the baby might be at maximum risk of being sensitized to allergens. From birth to about two years of age, the baby’s immune system is relatively immature and the layer of cells lining the digestive tract (known as the gastrointestinal epithelium) may be more permeable than in the mature human. From the age of 2 years onward, children appear to outgrow their early children food allergies. Based on research in animals, it is thought that tolerance to foods develops as the immune system matures and the lining of the digestive tract changes so that food molecules of the size required for an allergic reaction to occur cannot pass through the digestive tract tissues (the epithelium becomes less permeable).
Many experts believe that if a baby can be protected from becoming sensitized to the most highly allergenic foods when the immune system and the digestive tract are in the most vulnerable stage for allergy to develop, the incidence of lifelong food allergies children and potentially life-threatening anaphylactic shock reactions to foods will be reduced and hopefully entirely prevented. When a baby has been identified to be at risk for developing allergies babies, measures to reduce allergic sensitization might be implemented at birth and the problems associated with future food allergy may be significantly reduced. However, as we shall see in later discussions, experts disagree on the best way to avoid this early allergic sensitization.
