... -20C1) Usage: both hot and cold use--Hot use by microwave: Place the gel pack in a container first then move to ... . Remove water from heat. Immerse gel pack in water for 5 minutes.--Cold usage: Lay the gel pack flat in freezer for at least ... pain, sciatica, vertebral pain, improve mucous membrane scar after surgery--cold compress: physical therapy for traumatic hemorrhage, heatstroke, itch, headache, ...