 Special investigations may be indicated to rule out other causes of oral ulceration . These include blood tests to exclude anemia , deficiencies of iron , folate or vitamin B12 or celiac disease . However , the nutritional deficiencies may be latent and the 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. <unk> ) , and a trial substitution to an alternative drug may highlight a causal relationship . 
