Aphthous stomatitis near to the ulcer, described histologically as "perivascular cuffing". Aphthous stomatitis has been classified as a type of non-infectious stomatitis (inflammation of the mouth). One classification distinguishes "common simple aphthae", accounting for 95% of cases, with 3–6 attacks per year, rapid healing, minimal pain and restriction of ulceration to the mouth; and "complex aphthae", accounting for 5% of cases, where ulcers may be present on the genital mucosa in addition to mouth, healing is slower and pain is more severe. A more common method of classifying aphthous stomatitis is into three variants, distinguished by the size, number and location of
Aphthous stomatitis unknown and are thought to be multiple and varied from one person to the next. This suggests that there are a number of possible triggers, each of which is capable of producing the disease in different subgroups. In other words, different subgroups appear to have different causes for the condition. These can be considered in three general groups, namely primary immuno-dysregulation, decrease of the mucosal barrier and states of heightened antigenic sensitivity (see below). Risk factors in aphthous stomatitis are also sometimes considered as either host-related or environmental. At least 40% of people with aphthous stomatitis have a positive family