Mercury exanthem.

We have observed 9 male patients with a generalized rash following the topical use of an over-the-counter antiparasitic powder (MOM), containing ammoniated (11.2 g%) and metallic (4.2 g%) mercury, to treat phthiriasis (lice infestation). Primary and intensely erythemato-exudative lesions of the pubic region and genitals were associated with inverted erythema of the upper inner thighs and, in severe cases, involvement of the face, neck, trunk and major flexures. Eruptions included exanthematic, papulo-vesicular, purpuric and erythema-multiforme-like clinical pictures. 7 of the 9 cases presented with general malaise and pyrexia. A positive patch test reaction to ammoniated mercury was observed in all cases. There are probably 3 routes of powder exposure behind this type of rash: (i) direct skin contact; (ii) airborne skin contact; (iii) inhalation.