Patch test triggering recurrence of distant dermatitis: the flare-up phenomenon

A 37-year-old woman presented with a pruritic, vesiculobullous eruption on her neck in the region of an ebony pendant. Acute allergic contact dermatitis was suspected and treated with oral prednisone and hydroxyzine. Two months later, we performed a patch test on her back using scrapings from the pendant dissolved in a 5% petrolatum solution. Readings at 48 and 96 hours were strongly positive and confirmed allergic contact dermatitis. Coinciding with the positive results of the patch test, an eruption resembling the butterfly shape of her pendant developed on her chest. The wood of the pendant was identified as Diospyros ebenum J. König.