yeah it's ♥♥♥♥♥ of babylon

Looks like It's actually not because of an item, but rather because of losing hp down to 1 on higher levels. Above mom's heart level I think it is.

Actually, you just have to be in the womb, I activated it twice while in the scarred womb and it is rather effective... essentially increasing his damage output to immense levels by maxing the shot speed out, without impairing his damage. However, it only lasts for a single room.

In other words, he gets r e a l l y mad about his hair.