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Cantharidin Topical

pronounced as (kan thar′ i din)

Why is this medication prescribed?

Cantharidin is used to treat molluscum contagiosum (molluscum bumps; a viral skin infection that causes raised, pearl-like bumps on the skin) in adults and children 2 years of age and older. Cantharidin is in a class of medications called vesicants. It is not known exactly how cantharidin works to treat molluscum contagiosum.

How should this medicine be used?

Cantharidin comes as a solution (liquid) to apply to the skin by a healthcare professional at a doctor's office or clinic. It is usually applied directly to areas on your skin with molluscum bumps once every three weeks as needed

After the medication is applied to the skin, it should be allowed to dry completely (up to 5 minutes) before you leave your doctor's office. 24 hours after the medicine is applied to your skin, you should wash the treated area of skin with soap and water. Do not vigorously rub your skin or use a washcloth or other abrasive material to wash your skin.

Topical cantharidin should only be applied to skin and should not be applied to the mouth, nose, eyes, or genital areas.

Do not touch the treated areas of your skin or allow topical cantharidin to come in contact with your eyes or mouth for 24 hours after the medication is applied or until after it has been washed off the skin.

Topical cantharidin may cause severe eye injury if it comes in contact with your or your child's eyes, including scarring and ulcers in your eyes and permanent loss of vision. If topical cantharidin comes in contact with your or your child's eyes, flush the eye for at least 15 minutes and get emergency medical treatment.

Do not apply any topical products, including creams, lotions, sunscreen, or steroids to the areas of skin to be treated on the day of your treatment (before treatment) and for 24 hours after your treatment or until after the medication is washed off. Do not wrap or bandage treated areas.

Topical cantharidin may cause blistering or severe pain at the application site. If you have a severe reaction at the application site sooner than 24 hours after topical cantharidin was applied, wash the medication off of your skin with soap and water and call your doctor. Your doctor may tell you to take an over-the-counter pain medication such acetaminophen (Tylenol) to help with these symptoms.

Topical cantharidin is flammable, even after it has dried on the skin. Treated skin should not be exposed to fire or open flames during treatment and after treatment until the medication is washed off.

Talk to you doctor if you have any questions about your treatment with topical cantharidin.

Ask your pharmacist or doctor for a copy of the manufacturer's information for the patient.

Other uses for this medicine

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

What special precautions should I follow?

Before using topical cantharidin,

  • tell your doctor and pharmacist if you are allergic to cantharidin, any other medications, or any of the ingredients in cantharidin topical solution. Ask your pharmacist for a list of the ingredients.
  • tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take.
  • tell your doctor if you have or have ever had any other skin problems.
  • tell your doctor if you are pregnant or plan to become pregnant. If you become pregnant while receiving topical cantharidin, call your doctor.
  • tell your doctor if you are breast-feeding or plan to breast-feeding. If you are breast-feeding, your doctor will avoid applying topical cantharidin to areas of your skin that your baby could come in contact with.
  • tell your doctor if you smoke. Topical cantharidin is flammable. Do not smoke after your treatment until the medication is washed off of your skin..

What special dietary instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What side effects can this medication cause?

Topical cantharidin may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • lightening or darkening of skin at the place where cantharidin was applied
  • redness, itching, dryness, or scabbing at the place where cantharidin was applied

Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately:

  • pain, swelling, or blistering at the place where cantharidin was applied
  • skin breakdown or sores at the place where cantharidin was applied
  • painful, irritated, or red eyes or loss of vision if topical cantharidin comes in contact with eyes

If topical cantharidin comes in contact with your or your child's mouth or is swallowed and you or your child experience any of the following symptoms, call your doctor immediately or get emergency medical treatment:

  • decreased urination; discolored or bloody urine; swelling of the face, arms, hands, feet, ankles, or lower legs; or unusual tiredness or weakness
  • nausea; vomiting; diarrhea; stools that are black, tarry, sticky, or have blood or mucus; or abdominal pain and cramping
  • unusual bleeding or bruising
  • seizures
  • sudden weakness in the arms, legs, or neck; drooping eyelids; difficulty swallowing; or slurred speech

Topical cantharidin may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online ( or by phone (1-800-332-1088).

In case of emergency/overdose

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

If someone swallows cantharidin, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.

What other information should I know?

Keep all appointments with your doctor.

Do not allow children to lick or bite treated areas of skin. Topical cantharidin has ingredient that has a bitter taste to discourage young children from putting the medication in their mouths.

Topical cantharidin contains a violet-colored dye, which may temporarily cause your treated skin to be a violet color.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

Brand names

  • Ycanth®
Last Revised - 10/15/2023