Chancroid is a bacterial sexually transmitted infection (STI) caused by Haemophilus ducreyi that results in painful genital ulcers known as “soft chancres” (CDC STD Facts).

Chancroid is frequently confused with other STIs that cause genital sores, but it has distinct features. This infection is highly contagious and, importantly, is fully curable with the correct antibiotics.

This guide provides a clinical explanation of what penile chancroid is. We will cover its cause, how to identify its symptoms, and the definitive treatment options.

What Causes Chancroid on the Penis?

Chancroid on the penis is caused by a specific bacterium, Haemophilus ducreyi, which is transmitted through sexual contact and invades the skin through micro-abrasions (StatPearls – Chancroid).

How the Haemophilus ducreyi Bacterium Causes Chancroid

The Haemophilus ducreyi bacterium causes chancroid by entering microscopic breaks in the skin during sexual contact, then releasing toxins that destroy skin tissue, leading to an open ulcer.

The incubation period is typically 4 to 10 days after exposure. Chancroid is rare in the United States but is endemic in many tropical and developing regions, such as parts of Africa and Asia (WHO).

Risk Factors and Transmission of Chancroid

The primary risk factor for chancroid is sexual contact with an infected individual, with transmission being significantly facilitated by the presence of open sores, being uncircumcised, and co-infection with HIV.

• Sexual Contact: Spreads through vaginal, anal, or oral sex with an infected person.
• Skin-to-Skin Contact: The highly infectious fluid (pus) from the sore can transmit the bacteria through non-sexual physical contact.
• Uncircumcision: Uncircumcised men have a higher risk of acquiring chancroid, as the area under the foreskin can trap the bacteria.
• HIV Risk: The presence of chancroid ulcers significantly increases the risk of acquiring and transmitting HIV by providing an easy portal of entry for the virus (PMC – HIV & Genital Ulcers).

What Are the Key Symptoms of Penile Chancroid?

The key symptoms of penile chancroid are the development of one or more “soft chancres”—painful, pus-filled genital ulcers—often followed by painfully swollen lymph nodes in the groin known as buboes (DermNet NZ).

How to Identify a Chancroid Ulcer (The Soft Chancre)

A chancroid ulcer is identified by its key characteristics: it is very painful, has soft, ragged edges, and a greyish-yellow base, which distinguishes it from the painless “hard chancre” of syphilis.

Symptoms usually appear 4 to 10 days after exposure. The infection begins as a small, tender red bump that quickly becomes a pus-filled sore (pustule) and then ruptures into an open ulcer.

The ulcer’s characteristics include:

• Pain: The ulcer is characteristically very painful. This is the primary differentiator from the painless “hard chancre” of primary syphilis.
• Margins: It has soft, irregular, or ragged edges (undermined borders).
• Base: The base is usually covered with a gray or yellowish pus (purulent exudate) and bleeds easily when touched.
• Location: On the penis, they commonly form on the foreskin, coronal groove (behind the glans), or penile shaft.

Recognizing Associated Chancroid Symptoms

Associated chancroid symptoms include the development of buboes (swollen lymph nodes) in about 50% of cases, pain during urination, and potential scarring or phimosis in uncircumcised men (Medscape – Chancroid Overview). Buboes are painfully swollen lymph nodes in the groin.

• Buboes: In about 50% of infected men, the lymph nodes in the groin become painfully swollen, forming a pus-filled abscess called a bubo, which can rupture through the skin.
• Dysuria: Painful urination, especially if the ulcer is near the urethral opening.
• Complications in Uncircumcised Males: Untreated ulcers can lead to significant scarring and tissue destruction, potentially causing phimosis (inability to retract the foreskin).

How Do Doctors Diagnose Chancroid?

Doctors diagnose chancroid primarily through a clinical evaluation of the painful ulcers, combined with tests to definitively rule out other, more common STIs like syphilis and herpes (StatPearls – Genital Ulcers).

A definitive diagnosis by culturing H. ducreyi is difficult. This process is not widely available and requires special laboratory media to grow the bacteria.

Therefore, a probable diagnosis is often made based on these 4 factors:

1. One or more painful genital ulcers are present.
2. The patient tests negative for syphilis (via darkfield microscopy or serological tests).
3. The patient tests negative for herpes simplex virus (HSV) via PCR or culture from the ulcer.
4. The clinical appearance of the ulcers is consistent with chancroid (soft chancre, buboes).

(Source: CDC Treatment Guidelines)

What Is the Treatment for Chancroid?

The treatment for chancroid is highly effective and consists of a specific course of antibiotics, with the CDC recommending a single-dose regimen of Azithromycin or Ceftriaxone as the preferred, most reliable option (CDC Treatment Guidelines).

How Antibiotics Cure Chancroid

Antibiotics cure chancroid by eliminating the H. ducreyi bacteria, with the CDC-recommended single-dose regimens being the most effective treatment for ensuring patient compliance (Merck Manual Pro).

Single-Dose Regimens (Preferred):

• Azithromycin: 1 gram taken orally in a single dose.
• Ceftriaxone: 250 mg given as an intramuscular (IM) injection in a single dose.

Multi-Day Regimens (Alternatives):

• Ciprofloxacin: 500 mg orally, twice a day for 3 days.
• Erythromycin: 500 mg orally, three times a day for 7 days (CDC Treatment Guidelines, 2021).

Key Steps for Successful Chancroid Management

Successful chancroid management requires diligent medical follow-up, potential drainage of buboes, and the immediate treatment of all recent sexual partners to prevent reinfection.

• Follow-Up: A re-examination within 3 to 7 days is necessary to ensure the ulcers are beginning to heal.
• Bubo Management: Large, painful buboes may require surgical drainage (aspiration) to relieve pain.
• Partner Treatment: All sexual partners from the 10 days preceding symptoms must be examined and treated, even if asymptomatic.
• Abstinence: Abstain from all sexual contact until treatment is completed and the ulcers are fully healed.
• HIV Testing: All patients diagnosed with chancroid should be tested for HIV and syphilis.

How Can Chancroid Be Prevented?

Chancroid can be prevented by practicing safe sex, including the consistent use of condoms, and by limiting the number of sexual partners, which reduces the risk of exposure to Haemophilus ducreyi (CDC – STD Prevention).

Chancroid Prevention Checklist

• Practice Safe Sex: Using condoms correctly and consistently reduces the risk of transmission.
• Limit Sexual Partners: Reducing the number of partners lowers exposure risk.
• Wash After Sex: Gently washing the genitals after intercourse can help remove bacteria.

The most important action is to see a healthcare professional immediately for any painful genital sore. This ensures a correct diagnosis to differentiate it from syphilis or herpes and allows for the correct antibiotic treatment to begin.

Understanding that chancroid is a common, curable condition is the first step toward treating it quickly and preventing its spread. At Factbasedurology, we believe that clear, non-judgmental information about STIs is the best way to empower individuals to protect their health and the health of their partners.

Glossary of Clinical Terms

To ensure full clarity, this glossary defines the key clinical and scientific terms used throughout this guide on chancroid.