Approach

The goal of therapy is to eradicate the lesion and induce some degree of immunity against human papillomavirus (HPV) to prevent wart recurrence. There is no cure for common warts.

Because many common warts will regress spontaneously in immunocompetent patients, the option of watchful waiting is reasonable in some cases and should be discussed with the patient.[5]​ This should be considered especially in children, because treatment is uncomfortable and may not be tolerated.

The initial choice of therapy should take into consideration the type of wart, location, age of patient, occupation and hobbies, previous treatments and their outcomes, and compliance. Before making definitive conclusions about treatment outcomes, a 2 to 3 month sustained trial should be given with monitoring of compliance. Treatment should not be discontinued too quickly. Combination therapy often accelerates wart eradication and increases immune responsiveness.

Facial warts deserve special consideration. In immunocompetent adults, a single lesion is best removed surgically. Filiform warts are best treated with cryotherapy. Multiple small warts are difficult to treat, and may be best treated with topical imiquimod.

Initial treatment of common warts

First-line treatments include salicylic acid (with or without duct tape occlusion) and cryotherapy.[5][6][7][8][9] [ Cochrane Clinical Answers logo ]

Salicylic acid and debridement:

  • Daily application of salicylic acid-containing compounds may have similar efficacy to that of cryotherapy, with a cure rate as high as 75% for cutaneous warts.[5][10]​ Salicylic acid has been found to be superior to placebo, but a systematic review found that there was no clinically relevant difference in effectiveness between topical salicylic acid, cryotherapy, or a wait-and-see approach for plantar warts after 13 weeks.[11][12] One other study found that salicylic acid increased the clearance of warts from all sites, although it may be more effective for warts on the hands compared with warts on the feet.[9]

  • Adverse effects include local tenderness, skin erosion, and super-infection. Instruments used for debridement should not be placed on any other parts of the body for other purposes, in order to minimise the spread of infection.

Impermeable tape:

  • Occlusion of the wart with impermeable duct tape may be a simple and effective method of eradication, with response rates as high as 85% by week 8 for cutaneous warts.[6][7] However, some authors have found no clear effectiveness for duct tape occlusion compared with placebo.[9][13]

  • The mechanism of its effectiveness remains unclear. Occlusion may deprive the wart of the necessary nutrients and oxygen, and induce starvation, leading to death. Adhesive compounds in the tape may cause a mild allergic or irritant dermatitis, thereby priming the immune response against the virally infected keratinocytes.

  • A popular regimen is to repeat a cycle of 6 days of tape occlusion without replacement followed by 1 day off, until the wart disappears. While this approach is safe and simple, it can be challenging to keep the area occluded for 6 days, given continuous exposure to friction and water from hand washing or showers. Additionally, placing tape on the fingers may not be cosmetically acceptable for some patients. Furthermore, this approach may be inconsistent, as success rates have been variable in double-blind randomised placebo-controlled trials.[13]

Cryotherapy:

  • Cryotherapy can be a clinically-efficacious and cost-effective treatment for common warts.[6][8][10][12]​ However, only one trial has demonstrated cryotherapy to be more effective than both salicylic acid and placebo, and this trial only considered patients with hand warts. No significant differences in cure rates were reported at 2-, 3-, or 4-week intervals.[9] A meta-analysis of randomised controlled trials (mostly of low methodological quality) was unable to show that cryotherapy was statistically superior to placebo, but it did find that aggressive cryotherapy was significantly better than gentle cryotherapy for the treatment of cutaneous warts.[11] One randomised controlled trial, performing an intention-to-treat analysis, found that cure rates for cutaneous warts treated in primary care were 39% with cryotherapy, 24% with salicylic acid, and 16% with a wait-and-see approach after 13 weeks.[12] Cryotherapy was found to be the most effective therapy for common warts, but the trial was unable to find a clinically relevant difference in effectiveness between the three approaches for patients with plantar warts. A total of 49% of patients with common warts were cured with cryotherapy after 13 weeks compared with 15% of patients who used salicylic acid in petroleum jelly and 8% of patients who received no treatment, while 14% of patients with plantar warts were cured with cryotherapy after 12 weeks compared with 14% of patients who used salicylic acid.[14] From pooled evidence-based data, it is possible to conclude that significantly higher remission rates can be expected with cryotherapy when used in combination with salicylic acid.[15]

  • Adverse effects of cryotherapy include: blistering, pain, infection, hypopigmentation, hyperpigmentation, and lesional recurrence. Dyschromia and scarring often result if cryotherapy is not administered judiciously. Occasionally, cryotherapy gives rise to a doughnut wart, with central clearing and annular recurrence. Uncommon adverse effects include scarring, damage to the digital nerve of the finger or toe (from treating the lateral side of the digit too aggressively), and nail matrix damage (from aggressive cryotherapy of warts involving the proximal matrix).[1]​​

Silver nitrate:

  • Application of 10% silver nitrate solution can be a clinically-efficacious and cost-effective treatment for common warts.[16]

  • Adverse effects of 10% silver nitrate solution include temporary and transient brownish discolouration of the skin.

Resistant or recurring common warts

Local immunotherapeutic treatments serve as immune adjuvants, stimulating the cellular immune response against the HPV-infected keratinocytes. Such agents are best combined with a destructive modality, such as cryotherapy or surgical destruction.

  • Intra-lesional Candida antigen, subject to renewed interest for the treatment of recalcitrant warts, can be effective if administered by an experienced physician.[17][18][19][20]​ It acts as an immune adjuvant, stimulating an immune response against virally infected cells.[17]

  • Imiquimod, a topically applied immunomodulator that activates toll-like receptor 7, can be effective for both recurrent lesions and warts in immunocompromised individuals.[21][22]​ It may be incorporated into a variety of regimens. The goal of treatment is to induce a persistent moderate inflammation of the treated area, usually marked by a dark pink-to-red colour. When used once daily for 4 weeks, 90% of patients benefited from wart clearance.[21] It is important to note that once-daily application to some non-facial lesions may not be tolerated by the patient, and application may need to be alternated to every other day.

Wart removal with either cold-scalpel surgery or laser surgery is an effective modality, especially for resistant or recurrent lesions. Success rates of 65% to 85% have been reported.[2] Unfortunately, such lesions tend to recur after this intervention alone, with rates of 30% reported.[1][2]​ For this reason, this destructive modality is best combined with a topical adjuvant modality, such as topical chemotherapy or topical immunomodulation, for increased efficacy.

Immunocompromised patients with common warts

In immunocompromised patients, warts should be treated aggressively because some HPV types carry a high risk of transformation into squamous cell carcinomas.[23] First-line treatment should include topical immunotherapy, such as Candida antigen or imiquimod, or topical chemotherapy.

For patients with multiple lesions, oral acitretin or isotretinoin may be considered as an adjunctive treatment to aid with skin healing.[24][25][26]

Treatment of filiform warts

First-line treatment for filiform warts is cryotherapy. Metal forceps dipped into liquid nitrogen for 5 seconds and applied to the base of the stalk until the entire lesion is frozen may be the best approach. A single freeze-thaw cycle appears to be equally effective compared with two freeze-thaw cycles.[27] Cryotherapy should be repeated every 2 to 3 weeks, ideally immediately after the scab from the healed blister has sloughed off. Caution should be exercised in patients with a tendency to develop severe blisters, such as those with Fanconi anaemia, cryoglobulinaemia, poor peripheral circulation, and Raynaud's phenomenon.[1]

Second-line treatment is surgery (cold scalpel surgery, CO2 laser, or laser surgery with a pulse-dye laser).

Cold-scalpel surgery carries the risk of infection, scarring, bleeding, pain, and nerve damage, and should be carried out under sterile conditions with the use of local anaesthesia by an experienced physician.

CO2 laser produces complete ablation of the lesion. It also requires local anaesthesia, physician expertise, and proper vapour evacuation mechanisms. Side effects include scarring, nail dystrophy, and the generation of an infectious plume that may affect the patient, physician and others present in the treatment room. A smoke evacuator is mandatory for this procedure.[28]

Laser surgery with a pulsed-dye laser usually requires no anaesthesia. Treatment is performed with a short pulse duration and high energies, in order to induce thrombosis and small vessel vasculitis of the vessels feeding the wart, and to induce non-specific heat trauma to the wart itself.[29]​ Treatment produces purple-grey purpura, which turns into an eschar in 1 to 2 weeks. Treatment also generates a potentially infectious plume, and evacuation with a vacuum is necessary.

Topical imiquimod may be used as an adjunctive treatment cryotherapy or surgery to reduce the risk of recurrence. Daily application to some non-facial lesions may not be tolerated by some patients, so treatment should be modified to application every other day.

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