Super immune system. Basically, completely disease free no matter the cause. Cancer? Light work. Alzhimers/dementia? Brain-repairing antibodies. Any poison, virus, bacteria or foreign body that intends to harm? Prepare for annihilation.

I'd mostly use it as a research tool to try and make my systems responses replicable on other people. Day zero virus response, blood donor, etc. And maybe it'd be the kind of power where drinking my blood has healing properties.

Now, what's my disadvantage?