A 29-year-old woman developed allergic contact dermatitis from colophony 1 year after an allogenic bone-marrow transplant for refractory anaemia. The donor had a previous history of contact dermatitis from colophony, with a positive patch test. Although we cannot absolutely exclude active sensitization, it seems highly improbable because host immunity is severely restricted by the chemoradiotherapy used to prepare marrow graft recipients. The clinical data therefore suggest that sensitivity to colophony was passively acquired through marrow transplantation.