Institution: HCFMUSP- Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo. Hospital of Medical School of University of São Paulo.

Introduction: The mouth breathing can cause structural and functional alterations on the stomatognathic system. The most frequent causes of oral respiration are nasal and/or pharyngeall obstructions. Amongst nasal obstructions, allergic rhinitis is a disease which has been spreading. Even though there is a direct relation between rhinitis and nasal obstruction and the latter with functional alterations of the estomagnático system, few are the studies which observed such alterations in patients with rhinitis