Will a chancre (hard sore) become smaller after applying fusidic acid cream?
Nov 29, 2025
Source: Cainiu Health
Dr. Liu Wenmin
Introduction
In general, applying fusidic acid cream will not reduce the size of a chancre. Chancres are caused by infection with Treponema pallidum, the bacterium responsible for syphilis. Fusidic acid cream is effective only against certain bacterial infections and has no effect on Treponema pallidum, thus it cannot address the underlying cause. If a skin lesion resembling a chancre appears, self-medication should be avoided and prompt medical evaluation is necessary for accurate diagnosis. In daily care, keep the affected area clean and dry, and avoid friction or pressure.
Generally, applying fusidic acid cream to a chancre will not make it smaller. Chancres are caused by infection with *Treponema pallidum*, the bacterium that causes syphilis. Fusidic acid cream is effective only against certain bacterial infections and has no effect on *Treponema pallidum*, so it cannot address the underlying cause. The detailed explanation is as follows:
Chancres are a typical early manifestation of syphilis, presenting as painless ulcers with a clean surface, often accompanied by swollen regional lymph nodes. Fusidic acid cream is an antibacterial agent primarily used to treat skin infections caused by susceptible bacteria such as *Staphylococcus*. However, since *Treponema pallidum* is not susceptible to this medication, the drug cannot inhibit its replication or eliminate the pathogen, and therefore cannot reduce the size or promote healing of the chancre.
If secondary bacterial infection occurs at the site of the chancre—manifesting as redness, swelling, or exudation—applying fusidic acid cream may help control the superimposed infection and alleviate local inflammation. However, it has no therapeutic effect on the chancre itself. Effective treatment of chancres requires specific anti-syphilis medications, such as penicillin, which can eliminate the pathogen and facilitate ulcer healing.
When skin lesions suggestive of a chancre appear, self-medication should be avoided and prompt medical evaluation is essential for accurate diagnosis. Maintain cleanliness and dryness of the affected area in daily life, avoid friction or pressure, and prevent secondary infection. Practice good personal hygiene during treatment and avoid unsafe contact to prevent transmitting the disease to others.
