Causes of Similar Symptoms to Mouth ulcers. Research the causes of these symptoms that are similar to, or related to, the symptom Mouth ulcers: Mouth rash (15 causes) Throat rash (10 causes) Tongue color changes Skin pigmentation changes (72 causes) Viral infection; Oral candidiasis (30 causes) Herpes simplex; Aphthous ulcer (82 causes) Anemia (926 causes)