Warts and verrucas will normally heal themselves but for painful or embarrassing lesions, pharmacists can offer a range of home treatments, says Steve Titmarsh... 

 
Common or cutaneous warts are usually the result of an infection by human papillomavirus (HPV) and most frequently occur on the fingers and hands, as well as the soles of the feet where they are called plantar warts or verrucas. 
 
Around 80 per cent of people will be infected with HPV at some point, but most will never know as the infection does not usually cause symptoms.1 Around 40 per cent of people will have cutaneous warts during their lifetime.2 
 
Some types of HPV are associated with 99 per cent of cases of cervical cancer – the fourth most common cancer in women worldwide.3 However, common warts are caused by different types of HPV4 than those that cause cervical cancer, so the risk of developing cancer from genital warts is very low.5 Nevertheless people who have genital warts should go to a sexual health clinic for treatment.6  
 
HPV infects keratinocytes in the skin’s epidermis resulting in small growths. Cutaneous warts can be classified as (also see photo examples):7,8 

• Common wart (verruca vulgaris) – raised with a rough surface that resembles a cauliflower
• Flat wart or plane wart (verruca plana) – usually round, flat-topped, skin-coloured or greyish yellow
• Plantar wart — on the sole of the foot (verruca plantaris) – appearing as small black dots under hard skin
• Periungual wart — around the fingernails or toenails. 

Warts on the palms or soles of the feet can coalesce into larger plaques known as mosaic warts. Some warts may resemble fingers and can have a stalk – known as filiform warts – commonly seen on men’s faces and necks.8 
 
Seborrhoeic keratoses, also called seborrhoeic warts or basal cell papillomas, are benign and harmless. They are often pigmented, ranging from golden brown to almost black, and vary in size from less than one centimetre to several centimetres in diameter. These skin growths affect over half of men and more than one in three women in the UK. They occur more frequently in older people and vary in number from person to person. They are not related to viral warts or sebaceous glands.9 
 
Warts are spread by skin-to-skin contact or indirectly through contact with surfaces carrying the virus such as wet shower floors or swimming pools.10 It is not certain how long HPV can remain infectious outside the body, but a related bovine strain could be infectious for months or possibly years.4  
 
Although contagious, common warts are not life threatening. They can cause embarrassment for some and discomfort in around half of people who become infected. 
 
Around two-thirds of cutaneous warts clear by themselves with no treatment within two years and about 95 per cent will clear within four years. For some people it may take much longer (up to 10 years). For people who are immunosuppressed warts may be large, cover large areas of skin and be resistant to treatment.11 
 
The spread of warts can be minimised by:12 
• Covering warts with a waterproof dressing when swimming 
• Using footwear in shared showers 
• Not sharing shoes, socks or towels 
• Not scratching lesions 
• Avoiding biting nails or sucking fingers affected by warts 
• Keeping the feet dry and changing socks every day. 
 
Treatment 
If warts are painful or people feel embarrassed by their appearance, then treatment can be recommended. However, facial warts should not be treated at home – they should be treated by a dermatologist. Anogenital warts also need specialist treatment. 
 
OTC treatments are usually based on salicylic acid (15–50 per cent) applied topically. Although the evidence base for wart treatments is generally weak, trials suggest that salicylic acid formulations clear warts in almost half (49 per cent) of cases.4  
 
Evidence from trials of topical salicylic acid and cryotherapy using liquid nitrogen suggest they may be more effective for warts on the hands than those on the feet.13 
 
A small trial suggested that clear duct tape might be effective against warts but subsequent evidence from two larger trials suggests it is no more effective than placebo.13 Nevertheless, for verrucas, the British Association of Dermatologists says it might still be worth trying, especially in children.  
 
Instructions are to cover the wart with duct tape for six days, replacing it if it falls off in that time. Next, remove the tape and soak the affected area in lukewarm water, paring down the wart to remove any dead skin cells. The wart is then left uncovered overnight and the duct tape reapplied in the morning. The process can be continued for up to two months.14 
 
Individual products containing salicylic acid for topical treatment for warts will each have specific application instructions, but generally they should be applied once a day after the surface of the wart or verruca has been debrided and/or softened by soaking in warm water for five to 10 minutes. 
 
Patients should be advised not to be too vigorous when debriding the skin to avoid spreading the virus to unaffected areas. After peeling off any remaining film from the first application the process is repeated for subsequent applications. The skin surrounding the wart can be protected with soft paraffin or a plaster, being careful to apply treatment to the wart only.15 
 
Topical formulations of formaldehyde, glutaraldehyde or silver nitrate are also available OTC for warts on the hands and feet.16 OTC formulations containing ‘chemical freezes’ are also available.  
 

When to refer 
People should be referred for medical attention if:17,18 
• A wart is bleeding, painful or changes in appearance, or interferes with a patient’s daily activities  
• They have facial or anogenital warts 
• Warts cover a large area of skin, eg mosaic warts in the hands and feet 
• The diagnosis is uncertain 
• A wart persists and starts spreading despite treatment 
• They have verrucas and diabetes or poor sensation on their feet  
• They have a weakened immune system because of immune-suppressing drugs, AIDS or immune-deficiency disorder.  
 

Where and when not to use salicylic acid 
Products containing salicylic acid for topical use should not be used on:19 
• The face 
• Intertriginous or anogenital regions 
• Moles or birthmarks 
• Mucous membranes 
• Warts that have hair growing out of them, red edges, or an unusual colour 
• Open wounds, irritated or reddened skin, infected areas  
• Areas that do not heal well, such as neuropathic feet, or where blood circulation is poor 
• Children under 2 years old 
• Children or teenagers during or immediately after chickenpox, flu or other viral infections because of a theoretical risk of Reye's syndrome 
• Normal skin 
 
 
References 

1. https://cks.nice.org.uk/topics/warts-verrucae/background-information/definition

2. https://onlinelibrary.wiley.com/doi/full/10.1111/bjd.16248

3. www.who.int/health-topics/cervical-cancer#tab=tab_1

4. Sterling JC, Gibbs S, Haque Hussein SS, et al. British Association of Dermatologists’ guidelines for the management of cutaneous warts 2014. Br J Dermatol 2014;171:696–712.

5. www.cancerresearchuk.org/about-cancer/causes-of-cancer/infections-eg-hpv-and-cancer/does-hpv-cause-cancer

6. www.nhs.uk/conditions/genital-warts

7. https://cks.nice.org.uk/topics/warts-verrucae/background-information/definition

8. https://cks.nice.org.uk/topics/warts-verrucae/diagnosis/diagnosis

9. www.bad.org.uk/shared/get-file.ashx?id=231&itemtype=document

10. https://cks.nice.org.uk/topics/warts-verrucae/background-information/transmission

11. https://cks.nice.org.uk/topics/warts-verrucae/background-information/prognosis

12. http://www.pcds.org.uk/clinical-guidance/warts

13. Kwok CS, Gibbs S, Bennett C, et al. Topical treatments for cutaneous warts. Cochrane Database Syst Rev 2012;9:CD001781.

14. www.bad.org.uk/for-the-public/patient-information-leaflets/plantar-warts/?showmore=1&returnlink=https%3A%2F%2F

15. https://cks.nice.org.uk/topics/warts-verrucae/prescribing-information/topical-salicylic-acid

16. https://bnf.nice.org.uk/treatment-summary/warts-and-calluses.html

17. www.bad.org.uk/for-the-public/patient-information-leaflets/plantar-warts/?showmore=1&returnlink=https%3A%2F%2Fwww.bad.org.uk%2Fpatient-information-leaflets#.YBryyy2l39A

18. https://cks.nice.org.uk/topics/warts-verrucae/management/management

19. https://cks.nice.org.uk/topics/warts-verrucae/prescribing-information/topical-salicylic-acid