Suddenly swollen lips a bag may be related to trauma, may also be allergies, herpes simplex infection and other factors. 1. Trauma, if the lips are hit by an external force, it may lead to soft tissue damage of the lips and oozing of tissue fluids, thus a sudden swelling of the lips may occur. 2. Allergy, if the lips come into contact with substances that are easily allergic, may produce an allergic reaction, so there will be a sudden swelling of the lips, but also may produce itching, redness and swelling and other reactions. 3. Herpes simplex infection, some patients with herpes simplex infection due to contact with the herpes virus, may lead to skin lesions, so there may be a sudden swelling of the lips a bag symptoms. Usually need to pay attention to personal body care health care, pay more attention to rest, appear abnormal situation timely medical treatment.