Mouth ulcers in patients with syphilis are yellow or grayish-white in color. Syphilis is a sexually transmitted disease, syphilis spirochetes can enter the body from the skin, mucous membrane breaks, usually 2 ~ 3 days after the blood circulation spread throughout the body. In 2 to 4 weeks, the genital area began to appear pimples or rice-sized erythema, erythema slowly bulging, will form a soybean-sized to fava bean-sized hard knots, hard knots ulcerated, vesicles, oozing, these oozing liquid contains a large number of syphilis spirochetes, has a strong contagious. Oral ulcers, called noma, occur and are divided into lip and tongue noma. Chancre of the lip, which can occur on both the upper and lower lip, is characterized by swelling of the lip and surrounding tissues, which can form visible ulcers covered with a thin yellow crust, and is therefore hard to the touch. The chancre of the tongue, on the other hand, occurs in the anterior portion of the tongue and has a smooth, pinkish-red surface, sometimes covered with a grayish-white pseudomembrane, which is also hard to the touch. If you find a suspected syphilitic mouth ulcer, you should go to a dermatologist for treatment of syphilis.