US Pharm. 2011;36(8):15-23.
Patients often ask the pharmacist for advice about warts. It is imperative to inquire about the location and appearance of the lesions. Warts in some locations (e.g., hands, feet) can be self-treated, but warts in other areas (e.g., face, mucous membranes, genitals) require referral to a physician.
Etiology of Warts
An estimated 16% of the general populations suffers from warts.1 Warts, or papillomas, are caused by a group of viruses known as human papillomaviruses (HPVs).2,3 These double-stranded viruses stimulate basal cell division to produce lesions that are generally located in the upper epithelial tissues.1 There are more than 150 related viruses and over 200 subgroups represented in this group, but not all are responsible for causing warts.1,2 Warts on the hands and feet are not transmitted as readily as sexually related HPVs, usually being caused by HPV subtypes 1, 2, 4, 27, and 57.2,4 Thirty-five types are known to infect the genital tract, most commonly subtypes 16, 18, 31, 33, 45, and 59 for squamous cell carcinoma and adenocarcinoma of the cervix.4 Types 6 and 11 are commonly associated with warts in the anogenital area.4
Sexually transmitted HPV types that tend to produce cancers are referred to as high-risk or carcinogenic HPVs.2 HPV has been linked to cervical, anal, vulvar, vaginal, penile, and oral cancers.
Other animals can carry papillomaviruses, but they are specific to that species. Contrary to superstition, frogs and toads cannot carry the virus and thus cannot pass the virus on to human hosts.1
Epidemiology of Warts
Most types of warts exhibit an age-related epidemiology, occurring with greater frequency in those aged 12 to 16 years.1,5 There is also a different risk by gender, with females developing warts more often and earlier in life; incidence peaks at 13 years in females, but at 14.5 years in males.1 Immunodeficiency can also increase the risk for warts.5
Damaging the skin increases the risk of warts.5,6 Thus, walking barefoot is a clear epidemiologic indicator of those who will contract plantar warts.
Another risk factor is having existing warts, which is a predictor of future warts.1 Transferring a virus to oneself is known as autoinoculation. Patients with warts should be advised not to bite, pick, or otherwise damage them, as doing so can release viral particles. These particles can implant on adjacent skin surfaces and may eventually cause crops of warts in a closely circumscribed area. Biting a wart can allow the virus to implant on the tongue, mucous membrane, or lips. Children should be instructed not to bite their fingernails or pick at hangnails, as both of these nervous habits can lead to skin breakage and increase the risk of warts. Shaving can spread an existing wart to new areas.6 For this reason, the face in men and the legs in women are common attack sites.5
Patients may ask the pharmacist where or how they contracted the virus. HPV can have a long latency period (perhaps 8 months or more), so it is usually impossible to identify the causal location or behavior.3 Infected patients may have touched a wart on another person.5 They may have contacted a fomite (i.e., an object that may be contaminated with infectious organisms), such as a towel that an infected person used to dry himself. They may have walked barefoot in an area where an infected person walked with bare feet, the most common means by which plantar warts are spread. In this case, pharmacists can help identify such common wart inoculation sites as swimming pools, gyms, and communal shower stalls. Patients may recall a specific skin break that allowed penetration, such as tattooing or skin piercing.
Types of Warts
Common Warts: Common warts (verruca vulgaris) constitute 70% of all warts.1 They seldom cause pain or discomfort, unless they arise in a part of the body where repeated environmental contact or unpleasant friction with clothing continually abrades them.7 They are most often found on the fingers, around the fingernails, and on the backs of the hands, although they can infect any part of the skin.8 They grow outward (a type of pattern known as exophytic), and the raised round or oval surface has a rough appearance, much like that of a cauliflower.1,7,8 The color is dark, light, or occasionally black.7 Patients often notice small black dots in the wart. These dots have the appearance of small seeds, leading to their being referred to as seed warts. Although patients believe that these “seeds” are the causative agents of additional warts, they are actually coagulated blood vessels.1
Plantar Warts: Plantar warts are usually located on the sole of the foot, an area also known as the plantar surface.1,8 Continual pressure caused by walking pushes the wart inward, so that plantar warts are referred to as endophytic (growing inward). The pressure of walking causes discomfort that may be mild (like a rock in the shoe) or intensely painful, hampering such normal activities as walking and running.7 These warts may also exhibit black spots on the surface. Patients may develop several plantar warts that are connected beneath the skin surface, a condition known as mosaic warts.
Flat Warts: As the name implies, flat warts are flush with the surface of the skin.1,8 While they can be found on any section of the skin, they prefer men’s beards, women’s legs, and children’s faces. They are smaller than common warts, and tend to implant in large crops of 100 or more. Flat warts are more common in children, and they are actually quite rare in adults.7
Filiform Warts: The distinguishing characteristic of filiform warts is implied in the name, which means “thread-shaped.” These warts develop extensions that can rapidly grow out into surrounding skin.1,8 Common sites include the perioral and periorbital areas and the nose.
Subungual and Periungual Warts: When the patient has warts on the hands or feet, they may spread to the areas around the fingernails or toenails. They can also grow underneath the nails. Those beneath the nails are extremely difficult to cure.7
Genital Warts: Genital warts, also known as condyloma acuminata, are located on the genitalia, pubic area, between the thighs, inside the vagina, or in the anal canal.7 They carry a high viral load, so that as many as 65% of a patient’s sexual contacts will also become infected.3 Genital warts can cause cervical, anal, vulvar, vaginal, penile, and oropharyngeal cancers.9,10
Untreated warts often disappear without any treatment, a phenomenon known as spontaneous regression. However, the patient cannot predict whether this will eventually occur, and waiting for it allows the wart to spread the virus to the patient and to others. Therefore, it is preferable to seek appropriate care to remove the wart(s).
Nonprescription Medications: Nonprescription products are only safe and effective when treating common or plantar warts.1 Patients should not treat any other type of wart and should not apply wart products to birthmarks, moles, or unusual warts with hair growing from them. They should not treat warts on the face, mucous membranes, or genitals. Patients who wish to treat hand warts should be advised to keep the hands as dry as possible during treatment, as overhydration of the stratum corneum can facilitate viral release (with the exception of the suggested pretreatment soaking). Wart products should be avoided if the skin is irritated, infected, or erythematous. Patients with diabetes mellitus or poor circulation should not use them due to an increased risk of infection. The maximum time of use is 12 weeks. If the wart remains after this, the patient should be instructed to see a physician.
The only safe and effective nonprescription wart medication is salicylic acid.1,11 Preparations are available in gels or collodion-based liquids (5%-17% salicylic acid), patches (12%-40%), and a karaya gum/glycol patch (15%). Collodion-based liquids should not be used around fire or flame and must be tightly capped after use to prevent evaporation of the ether. If visible crystals appear in a bottle, it must be discarded. Patients should not inhale the vapors from collodion-based products. They should presoak the area for 5 minutes and dry it thoroughly before application of the product.
Salicylic acid is a keratolytic agent that slowly removes epidermal cells infected with HPV. The dosage forms also occlude the skin, and presoaking followed by occlusion aids the product’s action through maceration of the stratum corneum.
Liquids should be applied one or two times daily with the applicator. Patients may surround the wart with petrolatum to help prevent it from reaching healthy skin. Plasters/patches are cut to size, applied, and left on for 48 hours, after which a new one is applied.
Freezing Therapies: Physicians have long applied cryotherapy to cure warts. A typical regimen is liquid nitrogen at -196˚C (-321˚F) applied until the wart has a 2 mm white halo surrounding it.4 Some physicians continue this application until the halo has been present for 20 seconds. Pain and blistering are common.
Since 2003, manufacturers have marketed nonprescription products that purport to freeze warts off.1 These cryogenic wart removal systems are regulated as medical devices by the FDA.1 They include Compound W Freeze Off, Dr. Scholl’s Freeze Away, and Wartner.12 All contain dimethyl ether and propane, and the latter also lists isobutane. These products cannot reach the temperature achieved by liquid nitrogen, or they would be far too dangerous for OTC sales. They also carry numerous precautions to help ensure safe use, such as prohibiting use in children under the age of 4 years.1,12
Occlusion: Collodion-based products occlude the area, perhaps augmenting their efficacy. This has led to the widespread practice of placing duct tape over the wart. Despite positive reviews in the lay media, there is little evidence to support its efficacy.13
Which Warts Can Be Self-Treated?
Warts can appear anywhere on the body, although not all types should be self-treated. For example, you cannot self-treat warts on the face. Nonprescription wart products work by slowly eating into the area where they are applied. Eventually, they expose the wart and slowly destroy it. There is a slight chance that the skin might look abnormal after the wart is eradicated. If this were to occur on the face, it would be a permanent scar.
Similarly, you cannot self-treat warts on the mucous membranes, such as inside the nose or mouth. Wart products are only safely applied to the outer layer of dead skin, and mucous membrane is living tissue.
Finally, you must not self-treat warts of the genital area. They could be signs of a sexually transmitted disease and must be evaluated by a physician.
Be Sure It Is a Wart!
Before you try to treat a wart, you should be sure that it is not something else. Never apply wart products to birthmarks, as they could scar the skin. If the suspected wart has hair growing from its surface, it is best to seek medical advice, as warts typically do not exhibit hair growth. You should never try to remove a mole with wart products. Doing so could cause pain, bleeding, and scarring.
How Do You Use Nonprescription Products?
Legitimate nonprescription wart products all have salicylic acid as the active ingredient. You can choose from several dosage forms. Liquids are easy to use. You simply apply the liquid with the applicator supplied (usually a small brush) until the wart is covered. Make sure you do not get the product on healthy skin, as the salicylic acid will eat into healthy skin just as it does with the wart.
You may also choose a patch; these products are easy to use as well. Some are precut circles. You should first remove the adhesive, then center the patch over the wart, pressing it to ensure it adheres well. Other patches are small rectangles or squares that allow you to cut the size needed before pressing it over the wart.
Gels often come in plastic bottles that make it difficult to apply since you cannot see where the gel is in the squeeze bottle. You may accidentally apply too much. Ask your pharmacist if you have other questions.
How Long Does Treatment Take?
If your skin problem is really a wart, nonprescription wart products should begin to slowly eat it away. You should notice improvement within a week, and complete removal of the wart within a few weeks, although the exact time is dependent on the size of the wart, its location, and whether you apply the product exactly as directed.
You have a maximum time of 12 weeks to try to remove the wart on your own. After that time, you should see a physician. What you think is a wart could actually be a squamous cell skin cancer, melanoma, or any of several other conditions that require a physician’s intervention.
1. Pray WS. Nonprescription Product Therapeutics. 2nd ed. Baltimore, MD: Lippincott Williams & Wilkins; 2006.
2. Human papillomaviruses and cancer. National Cancer Institute. www.cancer.gov/cancertopics/
3. Juckett G, Hartman-Adams H. Human papillomavirus: clinical manifestations and prevention. Am Fam Physician. 2010;82:1209-1218.
4. Lipke MM. An armamentarium of wart treatments. Clin Med Res. 2006;4:273-293.
5. Warts: who gets and causes. American Academy of Dermatology. www.aad.org/skin-conditions/
6. Warts. American Academy of Dermatology. www.aad.org/skin-conditions/
7. Warts. PubMed Health. www.ncbi.nlm.nih.gov/
8. Warts: signs and symptoms. American Academy of Dermatology. www.aad.org/skin-conditions/
9. Colón-López V, Ortiz AP, Palefsky J. Burden of human papillomavirus infection and related comorbidities in men: implications for research, disease prevention and health promotion among
Hispanic men. P R Health Sci J. 2010;29:232-240.
10. Palefsky JM. Human papillomavirus-related disease in men: not just a women’s issue. J Adolesc Health. 2010;46(suppl 4):S12-S19.
11. Leung L. Recalcitrant nongenital warts. Aust Fam Physician. 2011;40:40-42.
12. Compound W Freeze Off. Dr. Scholl’s Freeze Away. Wartner. www.drugstore.com. Accessed July 5, 2011.
13. Wenner R, Askari SK, Cham PM, et al. Duct tape for the treatment of common warts in adults: a double-blind randomized controlled trial. Arch Dermatol. 2007;143:309-313.
14. D’Souza G, Kreimer AR, Viscidi R, et al. Case-control study of human papillomavirus and oropharyngeal cancer. N Engl J Med. 2007;356:1944-1956.
15. Syrjänen S. Human papillomavirus (HPV) in head and neck cancer. J Clin Virol. 2005;323(suppl):S59-S66.
16. Scully C. Oral squamous cell carcinoma: from an hypothesis about a virus, to concern about possible sexual transmission. Oral Oncol. 2002;38:227-234.
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