Medical Treatment of Plantar Warts
Start with salicylic acid 15-40% as first-line therapy, applied daily after paring the wart, for at least 3 months before considering treatment failure. 1, 2, 3
First-Line Treatment: Salicylic Acid
Salicylic acid (15-40%) topical preparations are the recommended initial treatment based on the British Association of Dermatologists guidelines, with the strongest evidence (Grade A recommendation). 1, 2
The mechanism works through promoting exfoliation of epidermal cells and stimulating host immunity against HPV. 2
Application technique is critical: Pare or debride the wart before each application to remove the thick keratin layer that prevents penetration, then apply the acid daily. 1, 2, 4
FDA-approved salicylic acid 6% is indicated specifically for plantar warts (verrucae plantares) as adjunctive therapy. 3
Important Reality Check
Plantar warts have inherently poor cure rates (14-33%) compared to warts at other body sites due to the thick cornified layer preventing adequate treatment penetration. 1, 2, 5
Treatment must continue for a full 3-4 months before declaring failure—this is not negotiable. 2, 4
Patient compliance is often poor due to surrounding skin irritation and the prolonged treatment course required. 4
Second-Line Treatment: Cryotherapy
If no improvement after 3 months of salicylic acid, switch to cryotherapy with liquid nitrogen applied fortnightly for 3-4 months. 1, 2, 4
Cryotherapy achieves approximately 14% clearance at 12 weeks, essentially equivalent to salicylic acid. 5
A high-quality 2011 RCT in BMJ found no difference between cryotherapy and salicylic acid (14% vs 14% clearance at 12 weeks, P=0.89). 5
Combination Therapy
More aggressive regimens combining salicylic acid with cryotherapy are probably more effective than either alone, though side effects are worse. 1, 2
This approach should be considered for resistant cases before moving to third-line options. 1
Third-Line Options for Resistant Cases
When both salicylic acid and cryotherapy fail after adequate trials:
5-Fluorouracil (5-FU) 5% cream under occlusion achieved 95% clearance in plantar warts treated for 12 weeks (Grade C recommendation, Level 2+ evidence). 1
Dithranol 2% cream showed 71% clearance of mosaic plantar warts within 10 months in case series. 1
Formaldehyde 3-4% solution as daily 15-20 minute soaks reported 80% cure rates in an open study of 646 children. 1, 2
Glutaraldehyde 10% solution showed 72% cure rate in resistant warts, but carries risk of deep necrosis with repeated application—use with caution. 1
Cantharidin-podophyllin-salicylic acid (CPS) combination achieved 97.82% cure rates in systematic review, though this is a specialized treatment. 6
Intralesional bleomycin showed 83.37% cure rates across studies. 6
Intralesional 5-FU 4% (with lidocaine and adrenaline) achieved 65% clearance with up to four weekly injections versus 35% placebo. 1
Alternative Treatments with Lower Evidence
Photodynamic therapy (PDT), laser therapy, hyperthermia, and topical immunotherapy are mentioned as options but have variable evidence. 1, 2
Imiquimod 5% cream showed total clearance in two case reports over 12 weeks, but lacks robust trial data for plantar warts. 7
Critical Pitfalls to Avoid
Never damage surrounding skin during paring—this spreads the infection through autoinoculation. 1, 8
Do not use salicylic acid in areas of poor healing or during varicella/influenza-like illness (Reye syndrome risk in children). 2
Avoid declaring treatment failure before completing 3-4 months of therapy. 2, 4
Be cautious with glutaraldehyde concentrations >10% due to necrosis risk. 1
Podophyllotoxin causes intense inflammatory reactions with blistering and is contraindicated in pregnancy—not recommended for plantar warts. 1