Chapter 37. Molluscum Contagiosum: Cantharidin Therapy

• • Parent’s or child’s desire for office-based treatment.

Absolute

• • Molluscum in facial, genital, or perianal area.

Relative

• • Previous cantharidin application with severe blistering.

• • Cantharidin 0.9% in flexible collodion.

  • Blunt-ended wooden applicator.

• • Pain.

  • Blistering.

  • Secondary infection.

  • Temporary hyperpigmentation or hypopigmentation.

• • Inflamed lesions should not be treated because they are resolving spontaneously.

  • If inflamed lesions are treated, they may blister more severely than uninflamed lesions.

  • Excoriated lesions do not need treatment. The central molluscum body has likely been mechanically removed.

• • Patient and parent education is crucial for a successful relationship with families of children with molluscum.

  • Although molluscum contagiosum is a self-resolving infection, parents may demand treatment.

  • If a physician defers treatment of a few molluscum and numerous lesions later develop, the parents may “blame” this often unpreventable spread on the physician.

  • Treatment does not prevent transmission or the development of new lesions.

  • An initial trial of treatment of a few lesions may be helpful in demonstrating the sequelae of therapy.

• • The patient should be comfortable and hold still for this therapy because moving may cause cantharidin to be applied in unintended locations and blistering may result.

• • Apply a small amount of cantharidin to the applicator and transfer this to the molluscum lesion (Figure 37–1).

• • Minimize contact with surrounding normal skin.

  • Ensure complete drying before the patient moves or dresses.

  • Treat a maximum of 20–30 lesions per visit.

  • Have the child bathe 4–6 hours after application.

  • • The treated areas can be washed with a soft washcloth and mild soap.

    • If child experiences blistering, discomfort, or burning within the first 4 hours, the areas should be gently washed sooner.

    • Scrubbing of treated areas is not necessary and should be discouraged.

• • The blister that occurs with cantharidin therapy may be painful.

  • • Apply antibiotic ointment to the areas twice daily until the blisters resolve.

    • Acetaminophen or ibuprofen can be given for pain.

  • Scarring, hyperpigmentation or hypopigmentation, and secondary bacterial infection may occur.

• • Follow-up is suggested in 2–4 weeks to treat new lesions.