You can cure Frostbite by Two Methods:
-Incantation - Bestial Constitution: Dropped by a Teardrop Scarab along the cliffside northeast of the Minor Erdtree in Dragonbarrow from Lenne's Rise, on the high ground almost directly west of the Rise and west side of the bridge.
- Throwfrost Blowse; Found in Mountain Tops of the Giants, Linurnia fo the Lake, Castle Sol