I was a little skeptical about it at first, and I didn't think it was working, then a friend of mine who uses them for her babies told me they kept it on all the time, during baths and bed time. I guess it activates better the more heat that's applied consistently. And once I stopped taking it off, we didn't even know when a tooth came in. There was zero drooling or chewing or fussiness. Every tooth is in before 18 months and never once did we ever have to give her anything for pain since there wasn't any!