Not only genetics and environmental factors are re-sponsible for the development of allergies. Epigenetic mechanisms – that are master regulators of gene transcription and thus of the accessibility and use of genome information – have been identied as a third power that is key in determining many features of
allergy. So far, three epigenetic mechanisms have been identied in humans: histone modication, DNA methylation, and posttranscriptional modi-cation by microRNA (miRNA) or small interfering RNA (siRNA). In recent years, it became clear that epigenetic regulation of gene function does not only play a role in the development of allergy but may also play a key role in the induction of tolerance against allergens, holding the promise to truly heal or pre-vent atopic diseases in the future.