Albumin is a protein produced by the liver and comprises 60% of proteins in human plasma. Human albumin (HA) is used in clinical practice for its oncotic and plasma-expanding properties. Non-allergic reactions precipitated by aggregation or denaturation of HA are described in the literature.1, 2 However, IgE-mediated allergic reactions to human albumin are extremely rare and only a handful of cases have been reported.3-5 Different diagnostic investigations are described, and standardization is lacking. We report a series of cases comprising five patients with hypersensitivity to HA and suggest a diagnostic algorithm.