What signs indicate infection to the wart area in a patient with sensitive skin or allergies treated with 5-fluorouracil (5-FU)?

Signs of Infection in Wart Areas Treated with 5-Fluorouracil

Monitor for purulent drainage, spreading erythema beyond the treatment site, systemic signs of infection (fever, malaise), and non-healing ulceration that persists beyond the expected timeframe—these indicate secondary bacterial infection requiring immediate evaluation and potential debridement of devitalized tissue. 1

Expected vs. Pathological Reactions

Understanding the difference between normal therapeutic inflammation and true infection is critical when using 5-FU for warts:

Normal Expected Reactions (Not Infection)

• Local inflammation, burning, rash, and erosions are expected pharmacological effects of 5-FU and represent the drug's therapeutic mechanism of damaging dividing basal cells 2, 3
• Mild to moderate pain or irritation at the application site is a normal therapeutic response 4
• Crusting, soreness, and superficial ulceration are common and often proportional to clinical efficacy 5, 2
• Blistering may occur as a less common but recognized adverse reaction 3

Signs Indicating Secondary Infection

• Purulent drainage from the treatment site suggests bacterial superinfection 1
• Spreading erythema that extends beyond the immediate treatment area indicates infection rather than localized inflammation 1
• Systemic signs including fever, chills, or malaise point to more serious infection requiring urgent evaluation 1
• Non-healing ulceration that persists beyond expected healing timeframes after treatment discontinuation, especially with devitalized tissue 1
• Deep tissue necrosis with black eschar formation suggesting full-thickness involvement beyond superficial inflammation 1

Management Algorithm for Suspected Infection

Mild to Moderate Inflammation (No Infection)

• Continue observation if skin remains intact despite inflammation 1
• Consider reducing application frequency or taking short treatment breaks to manage side effects 5
• Apply thin emollient to the area, which is permitted during treatment 5
• Weak topical steroid can be applied if reaction is excessive but not infected 5

Erosions Without Deep Tissue Involvement

• Discontinue 5-FU application immediately 1
• Allow healing by secondary intention with observation 1
• No debridement necessary if superficial only 1

Deep Ulceration or Signs of Infection

• Immediately discontinue 5-FU 1
• Evaluate for bacterial infection with clinical assessment 1
• Consider debridement only when devitalized tissue clearly prevents healing 1
• Deep necrosis extending beyond epidermis into dermal layers requires debridement 1

Special Considerations for Sensitive Skin

Patients with sensitive skin or allergies face higher risk of excessive reactions:

• Allergic contact dermatitis is a recognized adverse reaction to 5-FU and must be distinguished from infection 3
• Start treatment over small areas (4-10 cm²) with flexible frequency to establish tolerance, particularly in sensitive patients 5
• Use caution at poor healing sites such as the lower leg, which may require supervision or observation rather than intervention 5
• Patients with thin or fragile skin should be managed more conservatively due to poor healing potential 1, 2

Common Pitfalls to Avoid

• Do not mistake normal therapeutic inflammation for infection—counsel patients that local irritation is expected and necessary for treatment efficacy 2
• Do not continue treatment in the presence of true infection signs—purulent drainage and spreading erythema require immediate cessation 1
• Do not debride superficial erosions—only deep necrosis or non-healing ulceration with devitalized tissue requires debridement 1
• Avoid facial application where destructive reactions are more likely to cause scarring 4