What causes cold sores at the corner of the mouth?

Cold sores around the mouth are usually caused by infection with the herpes simplex virus. This virus can cause painful small blisters or sores around the lips, medically known as "herpes simplex" or "cold sores." Below are some factors that may contribute to the occurrence of cold sores: 1. **Viral infection**: The herpes simplex virus is the primary cause of oral herpes. It can spread through contact with the saliva or blister fluid of an infected individual. 2. **Weakened immune system**: When the body's immunity is compromised, such as during a cold, fever, high stress, fatigue, or menstruation, cold sores are more likely to recur. 3. **Sun exposure**: Prolonged exposure to sunlight can cause sunburn on the lips and increase the risk of developing cold sores. 4. **Lip injury**: Cuts, burns, or other types of irritating injuries make it easier for blisters to develop on the lips. 5. **Influenza**: The flu can also trigger the development of cold sores, and patients may experience additional symptoms such as fever and fatigue.