I guess they work by being worn against the skin. The baby's body temperature helps release an oil into the skin which is supposed to ease inflammation, and therefore, help reduce pain and fussiness in teething babies. A couple friends have sworn by these and even said they helped cut down on the drooling tremendously.
Since our little guy doesn't have any teeth yet (and probably won't for awhile since it's already been a month and this feels like forever!) I decided to give it a try and see if these things worked. I got him a necklace and ankle bracelet set. The necklace is just a little bit too big for this worrywart mama - it could probably get pushed up over his chin and get stuck. So I doubled it and put it around his ankle. Still loose. The ankle bracelet is a little too big, too - if he's not wearing socks or footie PJs,they both just come flying right off.
Within a few hours of wearing them, the drool dried up. It dawned on me while I was playing with Jacob that his chin was completely dry. That's great and all, but the drool was the least of my concerns. He's been wearing the amber now for about two weeks, and I'm not sure if I see any dramatic results. Some days are better than others, but I imagine that's just how it goes.