User blog comment:FairyRaven/Fairy Tail Chapter 414: Drops of Fire, Review and Commentary/@comment-5006572-20150105153905/@comment-1776824-20150105154508

I just hypothesized that Igneel could not create antibodies while frozen in time. .-.

Also, it is very possible that Igneel did not have enough antibodies created, which would mean Grandeeney and Metalicana would not have as well, by the time Tenrou Island was attacked. At this point they did and were just like, "Well oh shit bro, time to fight."