User blog comment:Miskos3/Fairy Tail 520: Dragon or Demon, Review/@comment-29874610-20170204151505/@comment-5303512-20170204230901

Wether or not it is inert is not the issue, the Demon Seed is still a physical part of Natsu, just like how a dragon seed is, because it physically changes the user, because it is demonic in nature still should be repelled by the temple. It is not hard to comprehend. The demon seed was basically confirmed part of Natsu when he got that growth. Porlyusica thought it was a tumor because of years of over exertion of magic, but she or Wendy should have caught it at an early time, not something that suddenly appeared.