[@Azereiah]

That's an interesting though. With their immune system theoretically non existant, absorbing blood directly could destroy basically everything if it's tainted. They're probably immune to autoimmune disease. They may still be susceptible to chance based on how the regeneration of cells occur. Probably still susceptible to infections but not viruses. Good for thought! 

I guess the next question is what about those who have blood disorders. Do they kill off the mages they can't drink from or do they just mark them as unusable?

[@Ellion]

I think the lore does specify the laws do state they can't use anyone under 18 because of strain and intimacy complications.