Molluscum Contagiosum

Molluscum contagiosum, otherwise known as water warts, a common viral infection to the skin, especially in small children affected by molluscum contagiosum virus. The infected skin raises alone or en masse anywhere in the body with watery, dome-shaped characteristic with or without a dimple in its center.

You get water warts through direct skin-to-skin contact, or indirect contact via something such as towels. In a swimming pool, direct contact between children or indirect contact such as taking turns using a floatation ring or other beach toys can cause infection. Pool water itself does not transmit water warts.

In many cases, the diagnosis of water warts is possible after a dermatologist recognizing the characteristic shiny, dome shaped bumps.

Physical removal of the water warts is a fundamental approach in the treatment of molluscum contagiosum. We treat water warts by directly pinching them off with special forceps. Direct removal, however, accompanies pain, and to reduce the pain during the procedure, we advise the patient apply a Lidocaine tape, an anesthetic tape (Penles® Tape) (photo 1) onto the warts prior to the procedure.

Rapid spreading of the warts in children or multiple warts formation in adults may suggest that the patient has a certain degree of skin barrier dysfunction such as atopic eczema. Immunodeficiency may also be an underlying cause in adults with multiple relatively large water warts.

After your child having the diagnosis of the water warts and the parents receiving the anesthetic tape, Penles® Tape at the clinic, please draw a line on the tape and cut it into approximately 1cm squares as shown in photo 1. After that, apply each piece onto each wart at least one hour prior to your appointment. Although Penles® Tape anesthetizes (a numbing tape) the area where it is applied, the extent of pain relief in each individual varies. Therefore, the maximum number of water warts that can be removed in one procedure is 15. Also please be informed that the procedure is limited to once a week.

If you have multiple warts, a single procedure may not be enough to eradicate the warts, and multiple procedures may be required. Even if all the water warts seem to be removed, new warts that have been in their latent phase may appear afterwards. Please be advised to carefully observe the skin even after seemingly complete disappearance of the warts.

As a novel topical therapeutic agent, Ycanth® was approved in Japan in 2025. Ycanth® uses cantharidin, a substance contained in a type of insect, which forms a blister when put on the surface of the skin. Ycanth® is thought to exert its effect against water warts by causing the adhesion between skin cells to be weak, forming a blister, and eventually shading the scab of the skin cells which are infected by molluscum contagiosum virus.

Topical treatment of water warts with Ycanth® is conducted once in every three weeks at medical institutes that deal with it, using a specific applicator (photo 2, and 3)
16 to 24 hours after Ycanth® being applied to the water warts, the site needs to be washed off with soap at home.

In a clinical trial of Ycanth®, 50 % of patients was reported to show complete disappearance of water warts in 12 weeks of Ycanth® treatment (with 4 treatments of Ycanth®).

As side effects, a blister, redness, and scab can appear on the site, as well as pain and itchiness can be perceived.
Photo 4 shows a treatment progress after topical application of Ycanth® onto the water warts.