After the vaginal opening on the medicine red pain is considered to be the local skin rupture, the wrong way to use the medicine, local medicine allergy and so on. 1. local skin ulceration: if the patient exists vaginitis and other conditions, causing local skin congestion and swelling, or even ulcerated, then it should be time to produce stimulation of the wound, pain and redness. 2. Wrong method of medication: If the method of medication is rough, then it causes damage to the mucous membrane, which can also cause pain. 3. Drug allergy: If you are allergic to the drug, then it can cause local edema, which can also lead to pain in the vaginal opening. If there is abnormal pain after using the medicine, then you need to consult a doctor in time and timely treatment.