Water of Brokilon

The Water of Brokilon is a psychotropic, mutagen-containing substance which can turn human girls into dryads. If applied early, they are fully transformed, but 10 yeas old and older girls will always have their human sweat instead of willow-smelling dryad one.

People with Elder Blood are apparently untouched by the process. When used on witchers it causes severe hallucinations and visions, but afterwards they are in full health.