What You Need to Know About the Signs and Treatment of Warts

Find out what causes warts and how to prevent them

An illustration of a wart.
An illustration of a wart. BSIP/UIG/Getty Images

Warts are actually benign tumors of the epidermis caused by a virus. The virus responsible is the human papillomavirus (HPV), a double-stranded DNA virus. The virus resides in the bottom layer of the epidermis and replicates into an almost normal-looking skin. Different sub-types of HPV cause different types of warts. Some human papillomavirus subtypes also cause cervical cancer and other more obscure types of wart-related cancers.

The Wart Root Myth

Contrary to popular belief, warts do not have "roots." They only grow in the top layer of skin, the epidermis. When they grow down, they displace the second layer of skin, the dermis. They do not grow into the dermis. The underside of a wart is actually smooth.

The Appearance of Warts

Warts normally grow out of the skin in cylindrical columns. These columns do not fuse when the wart grows on a thinner skin, such as the face. On thicker skin, the columns fuse and are packed tightly together giving the surface the typical mosaic pattern. Black dots can sometimes be seen in a wart. These are actually blood vessels that have grown rapidly and irregularly into the wart and have thrombosed or clotted off.

Who Gets Warts?

Warts can occur in people of all ages but occur most commonly in children and young adults. They spread by direct contact, simply by touching the wart. Warts normally resolve spontaneously but the time it takes for this resolution is variable.

Most warts resolve within weeks or months, but some may take years. It appears that a person's susceptibility to warts and the time it takes for them to go away is related to the individual's immune system. People who have immune-related diseases such as AIDS and lymphoma or who are taking chemotherapy tend to have more warts that last longer.

Salicylic Acid for Warts

Most warts can be treated with simple over-the-counter remedies. For those who are resistant to these measures, other types of treatments are effective.

Salicylic acid is a very common and effective over-the-counter treatment but requires consistent application every day. They best way to use salicylic acid is to first pare the wart with a blade, pumice stone, emery board or small scrub brush. Soaking the wart in warm water will aid in the absorption of the medicine.

Salicylic acid is applied to the wart and allowed to dry. The normal surrounding skin may be protected with petroleum jelly. Occluding the treated wart with a band-aid or piece of tape also improves the absorption of the medicine. This procedure should be repeated daily ideally around shower or bath time. Salicylic acid can be found in several forms, including a thick oil or incorporated into an adhesive plaster form.

Freezing Warts

Cryotherapy is another effective treatment of warts. A provider applies liquid nitrogen as a spray or on a cotton swab to the wart. This freezes and kills the affected cells. The connective tissue is not destroyed; therefore, the lesion usually heals without significant scarring.

The human papillomavirus is not killed by cryotherapy and is released into the surrounding tissue allowing the immune system to kill it. A blister typically forms on the site treated, crusts over and falls off. Since blisters are painful to walk on, cryotherapy is not the first choice for warts on the bottom of the foot.

Other medicines that may be applied to warts or injected into them include lactic acid, trichloroacetic acid (TCA), formalin, glutaraldehyde, cantharidin, podophyllin, Retin-A, and bleomycin. These treatments should be supervised by a health care provider.

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