Aphthous stomatitis is not considered to be true aphthous stomatitis by some sources. Some of these conditions may cause ulceration on other mucosal surfaces in addition to the mouth such as the conjunctiva or the genital mucous membranes. Resolution of the systemic condition often leads to decreased frequency and severity of the oral ulceration. Behçet's disease is a triad of mouth ulcers, genital ulcers and anterior uveitis. The main feature of Behçet's disease is aphthous-like ulceration, but this is usually more severe than seen in aphthous stomatitis without a systemic cause, and typically resembles major or herpetiforme ulceration or both. Aphthous-like ulceration
Aphthous stomatitis peripheral blood picture may appear relatively normal. Some suggest that screening for celiac disease should form part of the routine work up for individuals complaining of recurrent oral ulceration. Many of the systemic diseases cause other symptoms apart from oral ulceration, which is in contrast to aphthous stomatitis where there is isolated oral ulceration. Patch testing may be indicated if allergies are suspected (e.g. a strong relationship between certain foods and episodes of ulceration). Several drugs can cause oral ulceration (e.g. nicorandil), and a trial substitution to an alternative drug may highlight a causal relationship. Tissue biopsy is not usually