How are sores in your mouth transmitted?

Different methods: Some sores like cold sores and some internal ulcerations are viral, like herpes virus, and can be transmitted by contact. They can be spread to other areas of body or to other hosts(people). Other viruses like HIV or aids can be spread by contact usually through open wounds. Some sores like canker sores or lichen planis are due to auto-immune reactions, so they are not transmittable.