Food allergies result from abnormal immunological responses to the ingestion of or exposure to certain foods.
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These allergies may be broadly classified as either immunoglobulin (Ig)E-mediated or non-IgE-mediated reactions, with the former being more rapid in onset, usually presenting within minutes of ingestion. Food allergies are quite distinct from food intolerance, where the latter develops as a result of difficulties in digesting certain types of foods that lead to unpleasant intestinal reactions.
The most common types of food allergies are immunological responses to proteins found in cow-based milk, eggs, fish, shellfish, peanuts, tree nuts, soy, and wheat. Although some food allergies, like those to cow-based milk, maybe outgrown, those to foods such as nuts and shellfish are lifelong, and people affected should take the necessary precautions to avoid life-threatening reactions.
While there are no definitive answers to the increasing prevalence of food allergies over the last 3 decades, there are several theories in existence. Many of these are postulated on premises of hygiene, antioxidants, and dietary fats, among others. The development of food allergies may be seen in those with genetic susceptibility, and this has been illustrated in many studies.
Allergies run in families
Studies suggest that there may be a genetic predisposition to the development of food allergies. There is compelling evidence that implicates environmental factors in the pathogenesis of these allergies, and one’s chances of having a particular type of allergy are increased if one’s parents are also affected by the same allergy.
Research on the heritability of food allergies
A study done by Sicherer et al. on a small group of twins showed that there was a concordance rate of nearly 65% in identical twins with a peanut allergy, which was higher than the less than 10% seen among dizygotic pairs. These results were in line with the findings of heritability among other allergic diseases such as allergic rhinitis, atopic dermatitis, and asthma.
A study was done by Wang et al. in the Chicago Food Allergy, the study found that most of the children in their investigation had some type of food allergy. They were able to identify genes possibly linked to peanut allergy, which suggests that particular genomic regions harboring these genes on a particular chromosome pose a significant risk for the allergy. This was seen in approximately one-fifth of the population in their study.
In a genome-wide association study, the largest of its kind in the world involving food allergies, researchers investigated about 1,500 children from the United States and Germany, who have food allergies. Over 5 million genetic variations were studied in the participants compared against controls. A food challenge test was done to establish a true food allergy to the reported food to rule out possible intolerance. This study was able to identify five loci that increase genetic susceptibility to food allergies. Of these five loci, four were strongly correlated for those associated with other types of allergies.
Food allergies may have a genetic component, but allergy susceptibility appears to be influenced by genetic predisposition and environmental factors. It is important to remember that allergies within families may also reflect shared environmental conditions that contribute to the development of food allergies. There is still much to be done in terms of research establishing the link between genetics and food allergies, but contemporary data illustrates that greater clarity is on the horizon. This, in turn, will help with the optimization of management, and possibly even the prevention of food allergies. The evolution of genetic research offers this promise.