If blood comes out from between his teeth and enters his throat or he swallows it, if the blood is predominant, meaning he tastes it, his fast is invalidated and he must make it up, but there is no expiation on him. If the saliva is predominant, there is nothing on him. If they are equal, it is invalidated as a precaution, as mentioned in Bada'i al-Sana'i 2: 99, and Al-Sharnbalaliyah 1: 202.