[Caustic necrosis due to topical formic acid 85% (Objectif ZeroVerrue(®))].

BACKGROUND: Formic acid 85% constitutes the active substance of a new wart removal agent marketed in France under the name of Objectif ZeroVerrue(®), a product sold over-the-counter for adults and children aged over four years, and on a doctor's recommendation for children aged under four years. Its mechanism of action may involve cellular destruction through dehydration.

PATIENTS AND METHODS: Herein we report two cases of cutaneous necrosis following application of formic acid 85%. One case was severe, affecting the extremity of the middle finger and involving the underlying extensor apparatus in a girl aged 3 and a half years. This necrosis required the creation of a pedicled fasciocutaneous flap and temporary arthroereisis.

DISCUSSION: The precautions for use set out in the information leaflet for this preparation based on formic acid must be strictly adhered to by patients. In particular, only one application should be made per week, taking care to avoid adjacent skin. It is essential to suspend treatment if the skin is still erythematous after the previous application, and the treated area must not be occluded with bandages. Doctors must be aware of the risk of necrosis, since their recommendation is required for children under the age of four years.