Board Thread:General Grimm Discussion/@comment-114.71.100.55-20160428035319/@comment-1695916-20160429073522

Put it in the context of Chicken pox. We can only get it once in life, and after that, our body builds immunity from it so we can never get sick from it again (due to the help of our white blood memory cells).

Every Grimm's blood is the same in that they all contains a unique magical property that takes a Hexenbiest's powers away. It's like a magical virus that permanently takes away their power. After she lost her powers, she eventually acquired an immunity from it. It was only the matter of time she restored it, and since she was pregnant with Diana, that immunity passed on to her, too.

After that, Juliette snorted the hat later on, transferring the immunity towards hers, too, and ultimately, turning her into a hexenbiest, as well. This is because the hair sample of Adalind in the shapeshifting spell they used to turn Juliette to Adalind had traces of her DNA in it, or something along those lines. Sean's mom also warned everyone that the shapeshifting spell can tie two individuals in ways unknown, so that could also be a reason. Another reason might be the fact that the hat they used was tainted with Adalind's presence. This might be why Sean's mom was so hesitant of performing the Grimm-power-restoration ritual in Adalind's storage vault.

Hope this explained things!