The main causes of inner lip ulcers are as follows: 1, long-term malnutrition, lack of vitamin B or infection with bacteria and fungi, the inner mucosa of the lips may be extensively eroded, thus forming ulcers. 2, when suffering from mucosal diseases such as aspergillosis or aspergillosis-like, the mucosa of the lips may form bulky blisters, which may appear as irregular erosion surfaces after breaking. The wall of the blister recedes in all directions and can be torn off together with the surrounding normal mucosa, thus causing the trauma to expand.3. When the immunity of the organism decreases and lichen planus occurs, the lip and cheek mucosa is rough and multiple vesicles can be formed, accompanied by white reticulation or dendritic patterns.4. When the infection virus triggers herpetic stomatitis, the lip, cheek and tongue mucosa can form clusters of dense small blisters that can easily break down and produce large vesicles.