A chancre (/ˈʃæŋkər/ SHANG-kər) is a painless genital ulcer most commonly formed during the primary stage of syphilis. This infectious lesion forms approximately 21 days after the initial exposure to Treponema pallidum, the gram-negative spirochaete bacterium yielding syphilis. Chancres transmit the sexually transmissible disease of syphilis through direct physical contact. These ulcers usually form on or around the anus, mouth, penis and vagina. Chancres may diminish between four and eight weeks without the application of medication.