Food Intolerance and childhood asthma: what is the link?

Food allergies and asthma are increasing worldwide. It is estimated that approximately 8% of children aged <3 years have food allergies. Foods can induce a variety of IgE-mediated, cutaneous, gastrointestinal, and respiratory reactions. The most common foods responsible for allergic reactions in children are egg, milk, peanut, soy, fish, shellfish, and tree nuts. Asthma alone as a manifestation of a food allergy is rare and atypical. Less than 5% of patients experience wheezing without cutaneous or gastrointestinal symptoms during a food challenge. In addition to acute respiratory symptoms, a food allergy may also induce airway hyper-responsiveness beyond the initial reaction. This process can occur in patients who do not demonstrate a decrease in lung function during the reaction. Inhalation of aerosolized food particles can cause respiratory symptoms in selected food-allergic individuals, particularly with fish and shellfish during cooking and aerosolization. However, this has not been demonstrated with the smelling of, or casual contact with, peanut butter. Rarely, food additives such as sulfating agents can cause respiratory reactions. This reaction occurs primarily in patients with underlying asthma, particularly in patients with more severe asthma. In contrast, there is no convincing evidence that tartrazine or monosodium glutamate can induce asthma responses. Although food-induced asthma is rare, it is common for patients and clinicians to perceive that food can trigger asthma. Avoidance of specific foods or additives has not been shown to improve asthma, even in patients who may perceive that a particular food worsens their asthma.However, patients with underlying asthma are more likely to experience a fatal or near-fatal food reaction. Food reactions tend to be more severe or life threatening when they involve the respiratory tract. The presence of a food allergy is a risk factor for the future development of asthma, particularly for children with sensitization to egg protein. The diagnosis of a food allergy includes skin or in vitro testing as an initial study when the history suggests food allergy. While negative testing generally rules out a food allergy, positive testing should be followed by a food-challenge procedure for a definitive diagnosis. The CAP-RAST FEIA (CAP-radioallergosorbent test [RAST] fluoroenzyme immunoasssay system [FEIA]) is an improved in vitro measure that in some cases may decrease the need for food challenges. However, similar to skin testing and the RAST, there is good sensitivity but poor specificity, such that specific challenges are often warranted.