Molluscum contagiosum (MC) is a viral infection of the skin or occasionally of the mucous membranes. MC has no animal reservoir, infecting only humans, as did smallpox. However, there are different pox viruses that infect many other mammals. The infecting human MC virus is a DNA poxvirus called the molluscum contagiosum virus (MCV). There are 4 types of MCV, MCV-1 to -4, with MCV-1 being the most prevalent and MCV-2 seen usually in adults and often sexually transmitted. The incidence of MC infections in young children is around 17% and peaks between 2-12 years of age. MC affects any area of the skin but is most common on the body, arms, and legs. It is spread through direct contact or shared articles of clothing (including towels).

In adults, molluscum infections are often sexually transmitted and usually affect the genitals, lower abdomen, buttocks, and inner thighs. In rare cases, molluscum infections are also found on the lips, mouth, and eyelids.

The time from infection to the appearance of lesions ranges from 1 week to 6 months, with an average incubation period of 6 weeks. Diagnosis is made on the clinical appearance; the virus cannot routinely be cultured.