[quote=@Sep]
Debatable, and I guess it's upto Wraith. The difference between the two is blood healing requires blood, something physical, going into the body whereas magical healing would just give the body energy to expediate the healing on its own. Though as I said its really down to Wraith as a player, since its affecting his character.
[/quote]

This is more what I was thinking as well. The blood is a foreign agent 'attacking' the body, therefore the nanites would respond to it as a hostile. Magic doesn't really work the same way, nor does it really have anything physical to fight against. It's an energy, and one could argue that depending on the nature of the spell, the healing is being performed by magically boosting the nanites. 

[quote=@Dead Cruiser]
But would the nanites nullify [s]alien infection and assimilation[/s] Dandelion's Very Special Hug?
[/quote]

Same as the blood, the nanites would definitely treat alien infection and attempted assimilation as a hostile foreign agent and immediately begin attempting to nullify it.