What antibiotic is good for leg ulcers? A Pharmacological Guide

October 14, 2025 •

4 min read

Chronic venous leg ulcers affect up to 1% of adults in developed countries [1.3.4]. When these wounds show signs of infection, the question arises: what antibiotic is good for leg ulcers? Antibiotics are only recommended when clear symptoms of infection are present [1.6.2, 1.6.4].

Quick Summary

Antibiotics are prescribed for leg ulcers only when clinically infected, not for simple colonization. Oral antibiotics like flucloxacillin are a first choice, while topical treatments are generally less favored due to resistance risks.

Key Points

Antibiotics Aren't for All Ulcers: Antibiotics are only for clinically infected leg ulcers, not for routine healing or simple bacterial colonization [1.6.4].
Systemic is Standard: Oral (systemic) antibiotics are the preferred treatment for infected leg ulcers, not topical creams [1.2.3].
First-Choice Antibiotic: Flucloxacillin is the first-choice oral antibiotic for infected leg ulcers, targeting common bacteria like Staphylococcus aureus [1.2.3].
Allergy Alternatives Exist: For patients with a penicillin allergy, doxycycline or clarithromycin are effective alternatives [1.2.3].
Compression is Key: The most critical treatment for venous leg ulcers is compression therapy to improve circulation and address the underlying cause [1.5.1].
Identify True Infection: Treatment should only begin when there are clear signs of infection, such as spreading redness, increased pain, warmth, or pus [1.6.4].
Topicals Not Favored: Routine use of topical antibiotics is discouraged due to the risk of creating antibiotic-resistant bacteria [1.2.2].

Understanding Leg Ulcers and Infection

Leg ulcers are chronic, open sores that can be slow to heal, most commonly caused by poor blood circulation (venous insufficiency) [1.5.6, 1.6.1]. While most leg ulcers are colonized with bacteria, this doesn't automatically mean they are infected or require antibiotics [1.2.3]. Antibiotics are not intended to heal the ulcer itself but to clear a clinical infection that is impeding the healing process [1.5.1, 1.6.1]. The cornerstone of treatment for venous leg ulcers remains compression therapy to improve circulation, along with proper wound cleaning and dressing [1.5.1, 1.5.2].

A clinical infection requires a healthcare provider's diagnosis. Signs and symptoms that may warrant antibiotic treatment include [1.6.4, 1.6.9]:

Spreading redness or swelling around the ulcer
Increased pain
Localized warmth
Fever or feeling generally unwell
A green or unpleasant-smelling discharge (pus)

The Role of Bacteria

Leg ulcers can host a variety of bacteria. Studies show that Staphylococcus aureus and Pseudomonas aeruginosa are among the most frequently isolated pathogens [1.4.2, 1.4.6]. Other common bacteria include Enterococcus faecalis, Proteus species, and Escherichia coli [1.4.2, 1.4.3]. The presence of multiple bacterial species (polymicrobial infection) is also common [1.4.2]. In some cases, antibiotic-resistant strains like MRSA (methicillin-resistant S. aureus) can be present, requiring specialized treatment [1.2.2]. A healthcare provider might take a wound swab for microbiological testing if an infection is not responding to initial treatment, in order to identify the specific bacteria and their antibiotic sensitivities [1.2.3].

Systemic vs. Topical Antibiotics

When an infection is diagnosed, the primary treatment approach involves systemic antibiotics, which are taken orally or, in severe cases, given intravenously [1.6.4].

Systemic (Oral) Antibiotics

Guidelines from organizations like the National Institute for Health and Care Excellence (NICE) recommend oral antibiotics as the first line of defense for a clinically infected leg ulcer [1.2.3]. The choice of antibiotic depends on the likely bacteria, severity, and patient factors like allergies.

First-Choice: Flucloxacillin is a common first-choice antibiotic, as it is effective against Staphylococcus aureus, a primary culprit in these infections [1.2.3].
For Penicillin Allergies: If a patient has a penicillin allergy, alternatives such as doxycycline, clarithromycin, or erythromycin (especially in pregnancy) are recommended [1.2.3].
Severe Infections: In cases of severe infection or when a patient cannot take oral medication, intravenous antibiotics like flucloxacillin, co-amoxiclav, or others may be administered in a hospital setting [1.2.3]. A typical course of oral antibiotics for an infected leg ulcer lasts for seven days [1.2.3, 1.5.1].

Topical Antibiotics and Antiseptics

Topical antibiotics (creams and ointments applied directly to the wound) are generally not recommended for treating infected leg ulcers [1.2.2]. This is due to concerns about promoting antibiotic resistance and the potential for skin sensitization or allergic reactions [1.2.2, 1.6.7].

While some evidence suggests certain antiseptic preparations, like those containing cadexomer iodine, may be beneficial, evidence for the routine use of other topicals like honey or silver-based products is not strong [1.3.3, 1.3.7]. The decision to use a topical agent rests with the wound care specialist and is made on a case-by-case basis. Current evidence does not support the use of systemic antibiotics to simply promote healing in uninfected ulcers [1.2.7].


Treatment Approach	Description	Primary Use Case	Key Considerations
Systemic Antibiotics	Medications taken orally (pills) or intravenously to circulate through the body.	For ulcers with clear clinical signs of infection (e.g., spreading redness, fever, pus) [1.6.4].	First-line treatment for infection. Flucloxacillin is a common choice; alternatives exist for allergies [1.2.3].
Topical Antibiotics	Ointments or creams applied directly to the ulcer surface.	Generally not recommended for routine use due to risks of resistance and sensitization [1.2.2]. May be considered in specific cases of critical colonization [1.6.7].	Risk of developing bacterial resistance is a major concern.
Topical Antiseptics	Preparations like cadexomer iodine or silver dressings applied to the wound.	To reduce bacterial load on the wound surface. Some evidence supports cadexomer iodine [1.3.7].	Evidence for many antiseptic dressings, including silver and honey, is limited for improving healing rates [1.2.7, 1.3.3].
Compression Therapy	The application of firm bandages or stockings to improve blood flow.	The foundational treatment for all venous leg ulcers to address the underlying cause [1.5.1, 1.5.8].	Essential for healing and preventing recurrence; must be applied by a trained professional [1.5.1].

Core Principles of Management

It is crucial to understand that antibiotics are just one component of managing an infected leg ulcer. The comprehensive management strategy is multifaceted:

Treat the Underlying Cause: For venous leg ulcers, compression therapy is the most critical element to improve circulation and promote healing [1.5.1].
Wound Care (Debridement): A healthcare professional will clean the wound and remove any dead (necrotic) tissue or debris, a process called debridement. This creates a healthy base for the ulcer to heal [1.5.1, 1.5.7].
Appropriate Dressings: Simple, non-stick dressings are used to cover the ulcer, maintain a moist healing environment, and protect it [1.5.1, 1.5.7].
Leg Elevation: When resting, elevating the affected leg helps to reduce swelling and improve blood flow back to the heart [1.5.1].
Use Antibiotics Judiciously: Systemic antibiotics are reserved only for ulcers that show clear signs of a spreading infection [1.6.4, 1.6.5].

Conclusion

So, what antibiotic is good for leg ulcers? The answer is nuanced. No antibiotic is beneficial for a standard, uninfected leg ulcer, as they do not aid in the primary healing process [1.6.1, 1.6.4]. When a leg ulcer becomes clinically infected, a healthcare provider will likely prescribe a course of oral antibiotics, with flucloxacillin being a common first choice and alternatives like doxycycline available for those with penicillin allergies [1.2.3]. Treatment decisions must be made by a medical professional who can assess the wound, diagnose infection, and consider the patient's overall health. The most effective strategy combines the judicious use of antibiotics for infection with foundational treatments like compression therapy and diligent wound care to address the root cause of the ulcer.

For more detailed guidance, consult the NICE guideline on antimicrobial prescribing for leg ulcer infection.

Frequently Asked Questions

Antibiotics should only be used when a leg ulcer shows clinical signs of infection, such as spreading redness, localized warmth, increased pain, fever, or a foul-smelling discharge. They are not recommended for ulcers that are simply colonized with bacteria but not infected [1.6.4, 1.6.5].

According to NICE guidelines, the first-choice oral antibiotic for an infected leg ulcer is typically flucloxacillin, usually prescribed for a 7-day course [1.2.3].

No, the routine use of topical or over-the-counter antibiotic creams is generally discouraged for leg ulcers. This is due to the risk of promoting antibiotic resistance and potential skin sensitization [1.2.2, 1.6.7].

If you have a penicillin allergy, your doctor can prescribe alternative antibiotics. Common choices include doxycycline, clarithromycin, or erythromycin [1.2.3].

Antibiotics do not heal the ulcer itself. Their purpose is to treat an active infection that may be preventing the ulcer from healing. The primary treatments that promote healing for venous ulcers are compression therapy and proper wound care [1.5.1, 1.6.1].

The most common bacteria found in leg ulcer infections include Staphylococcus aureus and Pseudomonas aeruginosa. Other frequently found bacteria are Enterococcus faecalis and various Gram-negative species like Proteus and E. coli [1.4.2, 1.4.6].

A colonized ulcer has bacteria living on its surface without causing a host reaction or signs of infection. An infected ulcer occurs when bacteria invade the tissue, leading to symptoms like increased pain, spreading redness, swelling, and pus [1.5.8].