The role of regulatory T cells in the induction and maintenance of peripheral tolerance has received growing attention during the last years. Several subsets of regulatory T cells were described based on their surface markers and cytokine production, but nevertheless, there are no specific markers for any subsets and their classification relies on their suppression mechanism. It is unknown which of the subgroups of regulatory T cells is more important in the prevention and control of allergic diseases, being commonly accepted its importance in homeostasis.