Examples

Cantharidin is a chemical derived from the green blister beetle.

How It Works

Your doctor "paints" cantharidin on your wart and covers it with a bandage. This is generally painless. The cantharidin causes the skin under the wart to blister, lifting the wart off the skin. When the blister dries, the wart comes off with the blistered skin. You may feel some pain when the skin blisters. When you see your doctor again, he or she will remove the dead skin and the wart. If the wart isn't gone after one treatment, you may need another treatment.

Why It Is Used

Cantharidin is sometimes used if salicylic acid or freezing a wart with liquid nitrogen (cryotherapy) has not successfully eliminated it.

Cantharidin should not be used:

• On people with diabetes, peripheral arterial disease, or other circulatory problems.
• On moles, birthmarks, unusual warts with hair growing from them, warts on the mucous membranes, or open wounds.
• In combination with another chemical agent.
• On or near the genital area.

How Well It Works

Cantharidin may be effective against some warts that are resistant to other treatments. After the wart is gone, there usually is no scarring.

Side Effects

Cantharidin may cause:

• Tingling, itching, or burning within a few hours of applying it to the skin.
• Very tender skin for 2 to 6 days.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Cantharidin can be used to treat warts that are resistant to other forms of treatment. It is not approved by the U.S. Food and Drug Administration (FDA) for the treatment of warts.

Cantharidin is not well-researched or widely used.

Although cantharidin does not hurt when it's applied, the resulting blister can be painful.

Cantharidin has a low risk of scarring.

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