A secondary chancre is a type of sore that appears during the second stage of syphilis, a sexually transmitted infection caused by the bacterium Treponema pallidum. This sore is typically painless and can develop on various parts of the body, including the genitals, mouth, or skin. It is a sign that the infection has progressed and requires medical attention. In addition to the chancre, individuals may experience other symptoms such as fever, swollen lymph nodes, and a rash. Early diagnosis and treatment with antibiotics, usually penicillin, are essential to prevent further complications associated with syphilis.