It's unlikely to release the chemical that people talk about as your child ID unlikely to reach over a hundred degrees centigrade.
People will talk if unknown drug quantities, but it's E363 a food additive with no known toxic dose ( food agency website I'm posting from a phone or I'd reference) and we make it in our bodies as part of metabolism. Don't worry about the 'oh you don't know what drug you're giving brigade' as now you do.
As long as you use it as a complimentary therapy ie in addition to calpol then you're not forcing your child onto weird and woo alternatives to real drugs. Which can be illegal for serious illnesses and plain stupid for a child in pain.
People don't like them around necks, but I'm sure if a child had been strangled he'd hear about it with a daily fail link on every thread of this kind. And we haven't. Consider your own risk factors.
Some people think they look tacky. Some people don't.
I'm as woo as they come. For D2 who screamed most of the day and night for 3 weeks I used calpol, broken, bonjella, teething powders and finally while on holiday in southwold bolted into the amber shop. She stopped screaming the next night. But of course that was the calpol kicking in after weeks and purely coincidence.
Amber is soothing in crystal healing BTW. Woo!