Atopic eczema affects up to 30% of children and 10% of adults. Individuals with eczema have been shown to be at higher risk of many other conditions (other atopic conditions – asthma and hay fever, ADHD, depression, autoimmune conditions) and at decreased risk of others (psoriasis and some cancers). However, from these observational associations it is not possible to establish whether eczema is causally related to these other conditions (and hence whether effective early treatment of eczema would alter the risk of these conditions) or whether the observational associations could be explained by common mechanisms (pleiotropy) or even reverse causation (whereby the early manifestations of the other conditions might influence a child’s risk of eczema). These diverse mechanisms are important to disentangle as they have important and different implications for the direction of future research into management and novel therapeutics for eczema as well as these other conditions.

We have recently carried out the largest ever genome-wide association study of eczema, identifying 24 genetic risk loci in Europeans. Using a technique called Mendelian randomization it is possible to use these genetic instruments to investigate the ‘causal’ nature of the associations with other conditions and therefore establish whether early effective treatment of eczema would have long term health implications far beyond just that of the eczema itself, potentially influencing the risk of life threatening conditions. Through an increased understanding of genetic overlap between eczema and other conditions, this analysis also has the potential to identify novel therapeutic targets.