Iron deficiency is common and when oral treatment is not sufficient intravenous application is indicated. Hypersensitivity to intravenous iron nanomedicines is rare but does occur and little is known about the underlying mechanism but complement activation has been suggested.

This is a purely exploratory study as it is not yet known whether in vitro complement activation can be stimulated by titration with iron preparations. These data will provide first empirical evidence of whether and to what extent complement activation occurs in this population.

Inclusion Criteria:Group 1)

• adult participants from 18-65 years of age
• previous hypersensitivity reaction grades I-IV to intravenous ferric carboxymaltose (Ferinject) Group 2)
• adult participants from 18-65 years of age
• previous intravenous ferric carboxymaltose (Ferinject) and no hypersensitivity reaction Group 3)
• adult participants from 18-65 years of age
• previous hypersensitivity reaction grades I-IV to iron sucrose (Venofer) Group 4)
• adult participants from 18-65 years of age
• previous intravenous iron sucrose (Venofer) and no hypersensitivity reaction

Exclusion Criteria:

• Group 1)-4) • Autoimmune disorder or immune deficiency

participants with a previous hypersensitivity reaction to an iron nanomedicine application and participants without a hypersensitivity reaction to a previous iron nanomedicine application