My c4a ( compliment component 4a) test is very elevated ( 20,535). i was told this elevates in people with mold illness. can anything else raise level?

Interesting question: "mold illness" would be low on my list. Notably, C4a is produced upon activation of the complement system (C4 is cleaved to form C4a) which may occur in active autoimmune IgG disease, infection, malignancy and other problems. Fungal infection could conceivably cause it, but mold allergy certainly would not (IgE does not activate complement). If the bumps are hives, then urticarial vasculitis maybe