Split lip (also called cracked lip or lip fissure) is a painful tear, crack, or split in the skin of the lip, most often occurring on the lower lip but sometimes the upper lip or at the corners of the mouth. It typically results from dryness and chapping (due to cold/dry weather, dehydration, mouth breathing, or licking lips), trauma (e.g., accidental bite, blow to the mouth, dental injury, or aggressive brushing), angular cheilitis (inflammation and cracking at the mouth corners from fungal/bacterial overgrowth, nutritional deficiencies like iron or B vitamins, or drooling), or less commonly cold sores (herpes simplex virus causing blistering then cracking). The split appears as a red, raw linear break with possible bleeding, crusting, scabbing, or yellowish exudate if secondarily infected; it causes stinging, burning, or sharp pain when opening the mouth, eating, smiling, talking, or exposing to acidic/spicy/salty foods, and may recur chronically if underlying dryness or irritation persists.