A 38-year-old woman presented with a pronounced increase in symptoms and proliferation of urticaria pigmentosa (UP) after acute psychological stress, which was quantified using the Spielberger's State-Trait Anxiety Inventory. Immunohistochemical examination of a skin biopsy from a new UP lesion showed a large number of activated mast cells expressing corticotrophin-releasing factor receptor-1 (CRF-R1) and there was high serum CRF. This is the first documented report to our knowledge of UP worsening associated with acute stress, possibly through activation of skin mast-cell CRF-R1.