What causes herpes sores on the mouth?

Herpes sores appearing on the lips are usually caused by infection with the herpes simplex virus. This virus can cause small blisters around the lips or inside the mouth, commonly referred to as cold sores or fever blisters. The following are causes of blisters appearing on the mouth: 1. Internal heat: Blisters on the lips may result from endocrine abnormalities caused by excessive internal heat in the body, ultimately leading to blister formation on the lips resembling herpes. 2. Viral infection: If a patient develops blisters on the lips, it could be due to a viral infection causing abnormal changes and swelling in the mouth. 3. Mucous gland cysts: If a patient suffers from mucous gland cysts, these can cause blister-like sores on the lips. When mucous glands become blocked, swelling may develop, creating conditions similar to herpes outbreaks. 4. Traumatic mucosal blood blisters: Blisters on the lips might also be caused by traumatic mucosal blood blisters, which occur when an injury to the mouth does not heal completely, resulting in the formation of a blood blister.