In general, painless sore (chancre) can remain undetected inside the body and swollen or enlarged lymph nodes are the primary stage of infection. The bacteria usually entered genitals, rectum, mouth or lips.
These signs may occur from 10 days to three months after exposure, but usually within 2-6 weeks. The sore will heal or usually disappear within a few weeks without treatment, but the syphilis infection remains in the body. In some people, syphilis then moves to the secondary stage.
The secondary stage of syphilis typically starts with the development of a rash on one or more areas of the body. The rash usually does not cause itching and is characteristic of rough, red, or reddish brown spots both on the palms of the hands and the bottoms of the feet. However, rashes with a different appearance may occur on other parts of the body. Sometimes rashes associated with secondary syphilis are so faint that they are not noticed. Other symptoms of secondary syphilis may include fever, swollen lymph glands, sore throat, patchy hair loss, headaches, weight loss, muscle aches, and fatigue. The signs and symptoms of secondary syphilis will resolve with or without treatment, but without treatment, the infection will progress to the latent and possibly late stages of disease.

For more details: Syphilis Infection Lab Testing