Normally, saliva from a syphilis patient is not contagious when it comes into contact with healthy people. However, if a syphilis patient’s mouth is damaged and the saliva contains red blood cells, it may be contagious. However, it is limited to patients with syphilis stage I and II, and the probability of transmission is much lower for patients with syphilis stage III. Even if the saliva of a syphilis patient contains a small amount of red blood cells, it will not cause indirect infection, so don’t worry. If a healthy person has been exposed to the saliva of a syphilis patient, they can choose to use doxycycline hydrochloride orally for half a month, or they can choose long-acting penicillin for intramuscular injection, which can effectively prevent the syphilis spirochete from retransmitting to others through the red blood cells in the saliva.