The junction of the upper lip and the lower lip. Children's angular stomatitis is an inflammation that occurs in the corner of the mouth at the junction of the upper and lower lips. It is common in children and often occurs symmetrically. According to the related information on the doctor's website, we can know that the spatula joint is the area where the upper and lower lips are connected, and its connection point is called spatula. The corners of the mouth often rot. Clinically, we call it angular stomatitis, which is a general term for all kinds of inflammation that occur at the junction of upper and lower lips.