Why children develop allergies In a breakthrough for millions of allergy sufferers worldwide, a European study has determined genetic and environmental risk factors for developing allergies in childhood. This may eventually lead to preventative therapies. Health © Thinkstock Allergic diseases like asthma, rhinitis and eczema are associated with an overly sensitive immune system. Symptoms are triggered by antibodies called Immunoglobulin E (IgE) that under normal circumstances are present in minute amounts in the body. During allergy, IgE molecules bind to specific substances known as allergens and trigger inflammation of the lungs, nasal passages or skin. The EU-funded MEDALL (Mechanisms of the development of allergy) initiative aimed to understand the mechanisms that trigger allergies in children. By bringing together immunology and allergy experts, MEDALL identified several genetic and environmental factors that lead to long-lasting allergic conditions. Researchers collected clinical information and samples from thousands of children aged 4-8 years. They then determined which allergens or environmental conditions they were exposed to at an early age. Researchers identified specific changes in some patients' genes that were associated with the womb environment; particularly if their mothers smoked during pregnancy. This sensitised the children's immune systems and was linked to allergic disease and asthma later on in childhood. This information, combined with other analyses on changes in gene activity in allergic children, could be used to develop allergy biomarkers. These are easily measurable indicators of allergic disease or the propensity to develop allergies later in life. Using mouse models, MEDALL also highlighted the role of several immune system factors that either cause or dampen allergic reactions. One of these, Interleukin-21 (IL-21), regulates immune system cells and lowers production of the allergy-causing IgE. IL-21 is therefore a promising candidate for therapies designed to decrease inflammatory responses of the immune system. The MEDALL study has considerably improved scientists' understanding of why and how allergies develop, and which factors predispose children to develop over-sensitised immune systems. The innovative diagnostic tools and biomarkers developed by MEDALL can be used to predict allergy risk shortly after birth. This may allow early interventions like immunotherapies that could prevent allergy development later in childhood. Keywords Children, allergies, risk factors, immune system, Immunoglobulin E, IL-21
