Hello, my baby girl is around 8.5 months and she has this condition where her head sweats so much that her hair is soaked .. what could this be ?

Sweaty child: 1-3 % of infant get sweaty heads when they nurse,eat,and sleep It is probably under reported by parents . There is no know cause for Idiopathic hyperhidrosis and is probably a genetic trait in the families--ask your parents. If the infant is developing normally by peds dev/charts they just watch. There are other causes ,but not enough room to discuss--talk with your Peds Doctor

I do not know: Young infants generally generate a lot of body heat, and if you are keeping her bundled up as well, she simply may be sweating as she loses body heat through her scalp/hair, causing the wetness. Fevers can do the same thing, so just make sure she is not febrile. Best wishes.