“…An overall prevalence of 10-20% has been reported for the general population (Rennie et al, 1985;Scully et al, 2003), with a higher prevalence of RAS (56%) in selected groups, such as university students (Donatsky, 1973). Although hereditary (Ship, 1965;Shohat-Zabarski et al, 1992), dietary (Eversole, 1994), hematologic (Burgan et al, 2006), infectious (Barile et al, 1963;Sun et al, 1996), allergic (Boulinguez et al, 2003) and immunologic (Natah et al, 2000) factors have been implicated, their role as the main etiological factors in the pathogenesis remains to be elucidated. Furthermore, with the dramatic worldwide increase in patients with immuno-suppression caused by medical treatments, systemic diseases, or both, the prevalence of these conditions may be increasing.…”