Witcher blood isn't known to contain transformative properties. Mages would have experimented on us far more if so. [ He glosses over the implications of that statement. ] But crossed with the Singularity's potent magic...

[ Who can say? He's learned not to determine anything an impossibility anymore. There are traces of Elder Blood and other alchemy in his blood—and those are transformative.

Still, the why may not be as important as whether Dean is...himself. And in that, Geralt is fairly certain. ]

Unless he begins exhibiting strange behaviour, I'd not concern myself.

[ She knows Dean best—she'll probably notice if he acts oddly again. ]