Dishing the dirt on asthma: What we can learn from poor hygiene

Allergic asthma continues to represent a huge health burden worldwide and is largely treated by non-selective immunosuppressive drugs, which often prove ineffective. The hygiene hypothesis proposes that the increased incidence of allergy and asthma in Western countries observed in the last 50 years is due to environmental changes that include improved hygiene and a lack of infections. The immunological mechanisms that must underpin such an environmental impact on immune regulation remain to be defined, making it difficult to identify specific ways of preventing development of allergy and asthma in early life. In this article we will seek to review some of the pathways that might underlie the hygiene hypothesis in an attempt to provide targets for future asthma prevention.