Anaphylatoxins are complement fragments that trigger mast cell degranulation → histamine release → vasodilation, increased vascular permeability, and smooth muscle contraction.

Main anaphylatoxins: C3a, C4a, C5a.

Of these, C5a is the most potent → also a powerful chemotactic factor for neutrophils.

C1q, C4b, C9 are not anaphylatoxins.