Merck Manual

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Sheldon R. Morris

, MD, MPH, University of California San Diego

Reviewed/Revised Feb 2023

Chancroid is a sexually transmitted infection caused by the bacteria Haemophilus ducreyi, which causes painful genital sores.

Chancroid is a sexually transmitted infection (STI) that is rare in the United States and other high-resource countries, occurring primarily in low-resource countries in occasional, local epidemics. Chancroid is a common cause of genital ulcers in areas of Asia, Africa, and the Caribbean.

Symptoms of Chancroid

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 form a bubo (an enlarged and tender group of regional lymph nodes). They sometimes become matted together, in some cases forming a collection of pus (abscess). 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 also form in other areas of the skin.

Diagnosis of Chancroid

  • 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 are or 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.

People with chancroid are at high risk of syphilis and HIV infection, so if initial test results for these other infections are negative, doctors recommend that people with chancroid come back in 3 months to be tested again.

Treatment of Chancroid

  • An antibiotic

Several antibiotics, given either by mouth or as an injection, are effective for chancroid. The following may be used:

  • Ceftriaxone in a single injection into a muscle

  • Azithromycin, ciprofloxacin, or erythromycin taken by mouth in a single dose

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 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.

Prevention of Chancroid

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

Drugs Mentioned In This Article

Generic Name Select Brand Names
Ceftrisol Plus, Rocephin
Azasite, Zithromax, Zithromax Powder, Zithromax Single-Dose , Zithromax Tri-Pak, Zithromax Z-Pak, Zmax, Zmax Pediatric
Cetraxal , Ciloxan, Cipro, Cipro XR, OTIPRIO, Proquin XR
A/T/S, Akne-mycin, E.E.S., Emcin Clear , EMGEL, E-Mycin, ERYC, Erycette, Eryderm , Erygel, Erymax, EryPed, Ery-Tab, Erythra Derm , Erythrocin, Erythrocin Lactobionate, Erythrocin Stearate, Ilosone, Ilotycin, My-E, PCE, PCE Dispertab , Romycin, Staticin, T-Stat
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