Also known as canker sores and ulcers  mouth sores usually result from bite injuries or allergic reactions They can also be a symptom of an underlying health condition Unlike cold sores  which are caused by the herpes simplex virus (HS1 and HS2) and develop on the lips and the skin around the mouth  non-Herpes related mouth sores can form on the gums  tongue  lips  the lining of the cheeks and throat