DNA methylation is an epigenetic process that regulates immune cell differentiation, proliferation, death, and activation, and has been linked to the development of chronic inflammatory disorders. Changes in the methylation status of key genes have been related to the onset, persistence, and severity of respiratory illnesses. The activity of viral and bacterial colonisation can potentially alter the DNA methylation profile. Bacteria, particularly Staphylococcus aureus toxins, have been identified as inflammatory amplifying factors in chronic lower and upper airway disorders. This study highlights what is known about the function of DNA methylation alterations in chronic airway disorders and the role of bacterial infection in this process. Changes in DNA methylation, whether intrinsic or caused by allergen or infection, have been related to the pathophysiology of asthma and allergies. These methylation alterations may limit the generation of anti-inflammatory mediators while boosting the survival and activation of pro-inflammatory cells. They may also influence the immune response to bacterial infection, increasing their survival and pathogenicity inside the afflicted organism.

Understanding the inherent epigenetic mechanisms as well as the influence of the environment – for example, a bacterial infection in the development of airway disorders – would substantially enhance disease treatment and diagnosis.