Angular cheilitis occurs when the corners of your mouth are irritated, cracked, or sore. Other signs of this condition are itchiness, redness, and a swollen appearance. This skin condition occurs when saliva gets trapped in the corners of your mouth, causing the skin to crack, creating an opportunity for a type of fungus to grow. Other possible causes of angular cheilitis are also high-carb diets or a vitamin B deficiency. While this skin condition can clear up on its own, getting it diagnosed will rule out other possibilities and your doctor can prescribe you a medication to help speed up healing.