Hi,
I've just bought one for my 7mth old. She had her first 2 teeth come through together. Put it on her just after seeing the tip on one come through. She has been happy and only needed 1 dose of pain killer so far. Heard somewhere that if adults went through teething we would all be on morphine (???)
Anyway, even if it doesn't work it is harmless and looks good. It was inexpensive.