What is this skin condition?
Viral warts occur when the skin cells in the top layer of the skin ( keratinocyte cells) are infected by the human papilloma virus (HPV). There are up to 100 different types of HPV within the HPV family. HPV can infect either the normal cutaneous skin or the mucous membranes ( genital, anal and oral skin). In general certain HPV types affect the cutaneous skin and other types infect the mucous membranes. Individual HPV types can occasionally spread between the different types of skin. Whilst cutaneous warts are rarely a major health problem, genital HPV can increase the chance of developing of cervical, vulval or penile cancer. This article will focus on cutaneous HPV. Further information on genital HPV can be found via this link.
Why have I got it?
Cutaneous warts, especially on the hands and feet, are very common. They are especially common in childhood as children will be infected for a period of time whilst their immune systems mount a response to kill the virus. In the vast majority of cases cutaneous warts will disappear without treatment as they are killed off by the immune system. This can take time, sometimes up to 2 years. Whilst the infection is present the warts can be spread to other body sites and to other individuals. Spread of plantar warts ( sole of the foot) can be limited by wearing guard socks. These may be helpful within a shared house . At a public swimming pools there are so many people using the facilities who may have plantar warts that it is probably best not to think about it and not to draw attention to yourself. School children are no longer checked for plantar warts and are not made to wear guard socks as the infection is so common.
Once you have had cutaneous warts it is unusual to be re-infected although this may occur in adult life. Immunity to some viral infections can fade over time and re-exposure can occasionally lead to re-infection. Patients who have a suppressed immune system either due to medication or illness are more prone to cutaneous warts.
Comparing the treatment options
Before commencing any self treatment it is very important to be sure of the diagnosis. Some skin cancers can resemble viral warts and in adults it is recommended to have the diagnosis confirmed by a competent skin care professional.
Many of the treatments work by killing the infected keratinocyte skin cells.
Self-treatment
The first treatments to try are salicylic acid preparations. Salicylic acid is a mild acid which dissolves the superficial skin cells containing the virus. Effective treatment takes time. The dead cells need to be removed and the salicylic acid must be applied night after night. Products to try include compound W and wartner.
Over the counter 'freezing' treatments can be tried but they are often not really cold enough to have an effect.
Help from your GP
Cryotherapy. This is the application of liquid nitrogen (-197 degress celcius) to the skin to destroy the infected skin cells. This does hurt a little. The mechansim of action is not entirely clear but it is likely that the water in the cells is frozen causing cell wall damage and activation of cell death signals. Following liquid nitrogen treatment the skin will become red and swollen. Blistering may occur. Clinical studies investigating the benefit of liquid nitrogen have been performed. Surprisingly these studies have not shown any clear benefit over no treatment. The reason for this may be that:-
1. Many viral warts do resolve spontaneously
2. The liquid nitrogen treatments in the trials were not aggressive enough and did not trigger enough cell death.
Liquid nitrogen treatments needs to be done by experienced medical staff. Under-treatment is a waste of time and will achieve nothing. Over treatment can result in tissue damage and damage to underlying structures.
Help from a Dermatologist
Cryotherapy. A Dermatologist is more likely to be confident to deliver an optimal treatment with cryotherapy. You may be warned to expect a lot of swelling and even blistering. However, the skin heals up well after liquid nitrogen and this treatment can be very effective.
Surgery. The infected skin cells can be surgically removed using a scraping procedure called curettage and cautery. Under local anaesthetic the infected skin cells are scrapped away from the surface in combination with cautery to kill off residual cells at the base of the treated area. Recurrences may still occur after curettage.
Imiquimod (Aldara). This ointment was developed to treat genital warts. It penetrates the thin mucosal skin easily. It is less successful on cutaneous skin as it is not absorbed easily. It may work on facial skin but is often unsuccessful on hands and feet. When a cell is infected by the wart virus the cell produces proteins which are expressed on the surface of the cell. these proteins alert the immune system to the fact that the cell has been infected and the immune cells then attacks and kills the infected cell. Imiquimod enhances this process and increases the ability of your own immune system to identify and kill infected and abnormal cells. During a successful imiquimod treatment the treated area will become very red and inflammed as the infected cells are killed off. Treatment is needed for up to 6 weeks. Some patients have flu like symptoms and sometimes de-pigmentation of the skin can occur as the pigment cells can be damaged by the imiqumod triggered inflammation.