Risk of cancer in patients with medically diagnosed hay fever or allergic rhinitis.
Data on allergic conditions as risk or protective factors for cancer are controversial probably because most studies have used self-reported data on mixed groups of allergies in a case-control setting. We define cancer risks in medically diagnosed hay fever/allergic rhinitis patients in a nationwide cohort study. A total of 138,723 hay fever/allergic rhinitis patients were identified from three Sw