Merck Manual

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Sheldon R. Morris

, MD, MPH, University of California San Diego

Last full review/revision Apr 2020| Content last modified Apr 2020
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Chancroid is a sexually transmitted disease caused by the bacteria Haemophilus ducreyi, which causes painful genital sores.

In developed countries, chancroid is rare. In 2017, only 7 cases of chancroid were reported in the United States. But it is a common cause of genital sores throughout much of the developing world. Because chancroid causes genital sores, people who have it are more likely to become infected with and to spread the human immunodeficiency virus (HIV).


Symptoms begin 3 to 7 days after infection. Small, painful blisters form on the genitals or around the anus and rapidly rupture to form shallow, open sores with ragged edges. These sores may enlarge and join together. Occasionally, these sores become deeper and damage other tissues.

The lymph nodes in the groin may become tender, enlarged, and matted together, forming collections of pus (abscesses) called buboes. The skin over the abscess may become red and shiny and may break down and discharge pus from the lymph nodes onto the skin. Sores may form in other areas of the skin.


  • A doctor's evaluation

  • Culture of a sample of pus or fluid

Doctors suspect chancroid in people with one or more painful genital sores (ulcers) that have no obvious cause, especially if they have been in areas of the world where the infection is common.

Usually, doctors take a sample of pus or fluid from a sore and send it to a laboratory to be grown (cultured). However, culturing and identifying these bacteria are difficult, so the diagnosis relies more on symptoms and likelihood of being exposed to the infection.

Specific tests for chancroid are not readily available, but blood tests may be done to exclude other causes, such as syphilis and HIV infection.


The following general measures can help prevent chancroid (and other sexually transmitted diseases):

  • Avoidance of unsafe sex practices, such as frequently changing sex partners or having sexual intercourse with prostitutes or with partners who have other sex partners

  • Prompt diagnosis and treatment of the infection (to prevent spread to other people)

  • Identification of the sexual contacts of infected people, followed by counseling or treatment of these contacts

Not having sex (anal, vaginal, or oral) is the most reliable way to prevent sexually transmitted diseases but is often unrealistic.


  • An antibiotic

Several antibiotics are effective for chancroid. The following may be used:

  • Ceftriaxone in a single injection into a muscle

  • Azithromycin taken by mouth in a single dose

  • Ciprofloxacin taken by mouth for 3 days

  • Erythromycin taken by mouth for 7 days

If buboes are causing discomfort, doctors may make an incision to drain them. This treatment is done only if people are taking antibiotics to control the infection.

If initial test results for syphilis and HIV infection are negative, doctors recommend that people with chancroid come back in 3 months to be tested again for syphilis and HIV infection, which may also be present.

If sex partners have had sexual contact with the infected person during the 10 days before the person's symptoms began, they are examined and treated regardless of whether they have symptoms of chancroid.

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