Kara’s first-aid hack:
Use frozen hair gel as an ice pack (I’m fond of bright pink Dippity Do). Squeeze some into a quart- or snack-size Ziploc bag and toss it in the freezer. You should use corn syrup instead of hair gel for teethers and mouth injuries (just in case the afflicted person bites through the baggie). The advantage of gel or syrup over water is that the ice pack itself isn’t as hard when frozen.