LAUSR

seems evident that microbes play a pivotal role in this disease. Numerous reports have confirmed a strong link between AD and S. aureus, with increased severity linked to S. aureus colonization of the skin. The presence of S. aureus on the skin of infants, months before development of AD further reinforces S. aureus as a key player in AD pathogenesis. However, the essential questions remain unanswered. Does S. aureus play a role in the actual development of AD? Can changes in the microbiome of the skin be used positively in the treatment of AD? In this issue of the BJD, Tott e et al. investigate the microbiome in children (aged 0–18 years) with AD. Bacterial swabs were obtained from the nose and from lesional skin. They found an association between disease severity and microbial composition, not only for the skin, but also for the nose. Furthermore, they report a significant correlation between the nasal and skin microbiome, with two distinct profiles, so that specific species in the nose correlated with specific species on the skin. Previously, the association between skin and nose microbiome, and the relation to disease severity has been reported in adult patients with AD, and decreased bacterial diversity in relation to flares is reported in children with AD. These findings of disease severity linked to microbiome diversity interestingly fit very well into what we already know about AD from clinical observations: (i) S. aureus is strongly linked to disease severity; hence, when S. aureus is increased, the microbiome diversity is decreased; and (ii) environmental factors are essential regarding the development of AD, as well as flares, and we now know that the local environment, including consumer products, foods, medication/antibiotics etc., influences the microbiome composition. Years ago, the hygiene hypothesis was much debated – it was believed that our immune system needs exposure to microorganisms to develop properly. Today, with new and improved techniques available and a molecular understanding of the host–microbe interaction, we can begin to explain these clinically observed associations of bacterial and environmental impact on AD. Despite the exciting scientific advances in recent years, much is left to be revealed, including a possible interaction between the skin and gut microbiomes. However, research constantly brings new insights to the complex interaction between host and microbes, hopefully emerging into new treatment strategies and more personalized medicine to the benefit of the patient.