A Chinese acupuncturist taught us about using FINE ground salt for dropping fevers. Fill the belly button cavity with fine ground salt (use a mortar and pestel if you have one to get it ground nice and fine so it doesn't irritate the sensitive skin), preferably sea salt, and cover well with skin tape (first aid type) or a couple of band-aids. Drink plenty of water and try to get some sleep. Good to do over night, then take a little break by cleaning the belly button out with water, drying gently and applying a tiny bit of oil (coconut, olive, jojoba, or castor). Repeat as needed after a few hours. Works well and is the go-to in our family.