BACKGROUND: Tacrolimus applied locally is a non-steroid anti-inflammatory drug with proven efficacy in atopic dermatitis. Skin infections can occur, especially viral infections. CASE-REPORT: A 35-year-old male patient had been treated for extensive atopic dermatitis for several months with tacrolimus (Protopic). After six months of treatment, he presented a large eruption of molluscum contagiosum, in particular on the zones that had received a substantial amount of tacrolimus. The treatment was discontinued and application of a preparation containing cidofovir led to the patient's quick complete recovery, without recurrence in the ensuing months. DISCUSSION: Viral skin infections, in particular poxvirus infections, are prompted by topical immunosuppressant treatments such as tacrolimus, usually in dose-dependent fashion. Paradoxically, they provide protection against bacterial infections by restoring the integrity of the cutaneous barrier. Application of cidofovir successfully treated a severe form of molluscum contagiosum rapidly without any noticeable adverse effects. This confirms several observations about the efficacy and the good safety of this drug in the treatment of infections by DNA viruses. It provides an additional therapeutic prospect for immunodepressed patients who often present extensive and resistant forms of infections that are usually common.