In the pathogenesis of allergic asthma/rhinitis, 2 main types of cells play a role: hematolymphatic cells (mast cells, eosinophils, T cells, B cells) and nonhematolymphatic cells (airway smooth muscle cells, epithelial cells). It is not known which one of the 2 cell types plays the primary role. Here we review the literature on allergic disease transfer and potential cure with allogeneic hematopoietic cell transplantation (HCT), as transferability and curability would support a primary role of hematolymphatic cells and have implications for donor selection for HCT and possible future treatment of severe allergic disease with HCT. A total of 18 nonallergic recipients were reported to develop allergic disease after transplantation; however, conclusive information for transfer was available for only 5 cases. Allergic disease was reported to abate in 3 allergic recipients; however, conclusive information for "cure" was available for only 2 cases. Problems in interpreting the reports include incomplete data on allergic disease in the donor or recipient before transplantation, not knowing the denominator, and the lack of controls. In summary, review of the literature generates the hypothesis that allergic disease is transferable and curable with HCT. A prospective study, including appropriate controls, is needed to evaluate this hypothesis.