What is the recommended treatment for common, plantar, or flat viral warts, including first‑line and second‑line options?

Treatment of Viral Warts (Common, Plantar, and Flat)

Start with topical salicylic acid 15-40% applied daily after paring the wart, continuing for a full 3 months before declaring treatment failure; if unsuccessful, switch to liquid nitrogen cryotherapy every 2 weeks for 3-4 months. 1, 2

First-Line Treatment: Salicylic Acid

Salicylic acid (15-40%) is the recommended initial therapy for all cutaneous warts because it is safe, accessible, and supported by meta-analysis showing treated warts are 16 times more likely to clear than placebo (49% cure rate vs 23%). 2, 3

Application Protocol

• Pare or debride the wart before each application to remove the thick keratin layer that blocks drug penetration—this step is critical for efficacy. 1, 2, 3
• Apply the salicylic acid preparation once daily after paring. 2
• Consider occlusion with a bandage after application to enhance penetration. 2
• Continue treatment for a minimum of 3 months before judging the regimen ineffective; premature discontinuation reduces cure chances. 1, 2
• Avoid damaging surrounding healthy skin during paring, as injury can spread HPV to adjacent tissue. 1, 2

Site-Specific Modifications

• Plantar warts: Use 15-40% salicylic acid paints or ointments; cure rates are lower (approximately 33%) due to thicker cornified layer requiring more aggressive paring. 1, 2, 4
• Hand/common warts: Use 15-40% salicylic acid paints or ointments. 1, 3
• Plane (flat) warts: Use lower concentrations (2-10% cream/ointment or 12-17% paint without occlusion) to minimize scarring risk on face/hands. 1, 3
• Facial warts: Salicylic acid paints are contraindicated due to chemical burn risk; use 2% cream cautiously if needed. 3

Safety Considerations

• All but very low-strength salicylic acid can cause chemical burns; avoid use in areas of poor healing such as neuropathic feet. 3
• In children under 12 years, limit the treatment area to prevent systemic salicylate absorption and toxicity. 2
• Monitor for salicylate toxicity signs (tinnitus, nausea, vomiting, hyperventilation, confusion) if treating large areas. 2
• Avoid use during varicella or influenza-like illness due to Reye syndrome risk. 2

Second-Line Treatment: Cryotherapy

If salicylic acid fails after 3 months, switch to liquid nitrogen cryotherapy applied every 2 weeks for 3-4 months (6-8 sessions total). 1, 2, 4

Efficacy and Technique

• Cryotherapy achieves 30-39% cure rates for plantar warts and 46% for hand warts, lower than salicylic acid for some sites. 4, 3
• More aggressive freeze regimens may improve efficacy to 65% but increase pain, blistering, and scarring risk. 4
• Use milder freeze settings in children to minimize pain and blister formation. 2
• Avoid cryotherapy in patients with diabetes, impaired circulation, or near nerves/tendons. 4

Combination Therapy

When monotherapy fails, combine daily salicylic acid application with fortnightly cryotherapy, acknowledging higher risk of local side effects (irritation, blistering). 1, 2, 4

• Combination therapy may achieve 86% clearance in some studies, though data quality is limited. 4
• More aggressive combination protocols increase efficacy but also increase adverse effects. 1, 2

Third-Line Options for Recalcitrant Warts

When both salicylic acid and cryotherapy have failed after adequate trials:

Topical Chemotherapy

• 5-Fluorouracil 0.5% combined with 10% salicylic acid yields 63% clearance vs 11% with salicylic acid alone in meta-analysis. 2
• Topical 5-FU under occlusion achieves 95% clearance in adult plantar warts after 12 weeks. 4

Alternative Destructive Agents

• Formaldehyde 3-4% solution as daily 15-20 minute soak produces approximately 80% cure rate in pediatric plantar warts. 2, 4
• Glutaraldehyde 10% solution achieves roughly 72% cure but carries risk of deep tissue necrosis with repeated use. 2, 4
• Dithranol 2% cream achieves 56% cure rate vs 26% with salicylic acid/lactic acid combination. 2

Immunotherapy

• Contact immunotherapy with diphenylcyclopropenone (DPC) shows 88% complete clearance with median treatment time of 5 months in retrospective review. 4
• Intralesional 5-FU (4% mixed with lidocaine/adrenaline) weekly for up to 4 injections achieves 65% clearance vs 35% with placebo. 2

Special Populations

Children

• Warts in children often resolve spontaneously within 1-2 years (50% at 1 year, 65% by 2 years). 1, 2
• Salicylic acid 15-40% remains first-line, but watchful waiting is reasonable given high spontaneous resolution rates. 2
• Avoid painful treatments in young children when possible; salicylic acid is generally well-tolerated. 1, 2

Immunosuppressed Patients

• Treatment may not result in cure but can reduce wart bulk and functional problems. 1
• Use standard treatments (paring, salicylic acid, destructive methods) while avoiding damage to surrounding skin. 1

Critical Pitfalls to Avoid

• Do not discontinue salicylic acid before completing 3 months—premature cessation is the most common cause of apparent treatment failure. 1, 2
• Do not skip the paring/debridement step—the thick keratin layer prevents drug penetration, especially in plantar warts. 1, 2, 3
• Do not treat large areas simultaneously in children under 12 to avoid systemic salicylate toxicity. 2
• Do not pare aggressively enough to injure surrounding skin, as this spreads HPV infection. 1, 2
• Avoid surgical excision—it has Level 3 evidence with Strength D recommendation (lowest rating) and lacks high-quality supporting studies. 4

Adjunctive Measures for Plantar Warts

• Refer patients with gait-related knee pain to physiotherapy for gait assessment and rehabilitation. 4
• Use cushioned footwear and temporary orthotic support to reduce pressure and normalize gait during treatment. 4
• Monitor for treatment-related infections, which occur in approximately 12% of patients. 4

Expected Outcomes and Realistic Expectations

• Plantar warts have inherently lower cure rates (14-33%) compared to warts at other body sites due to thick plantar skin. 4
• Patient compliance is often poor due to surrounding skin irritation and prolonged treatment courses required. 4, 3
• Spontaneous resolution occurs in approximately 30% of cases within 6 months, though waiting may not be acceptable if the wart causes pain or functional impairment. 4