As I am not an expert on molds or how they thrive or are killed, or how harmful they may be to ingest in small amounts, I can't say how safe it is to use, but the duck DOES get liquid inside of it, and there is no way to get it out. I don't use this infuser anymore for a few reasons:
It's a little too small for the amount of tea I steep
It gets all brown around the duck and doesn't look as cute as when you first get it (this is not a deal breaker, I'm just saying...)
The liquid inside skeeves me.
My other infuser just broke, so I will use it for the next couple of days while I wait for a new one to arrive (the liquid inside skeeves me, but I guess not being able to have my tea today is worse!)
So, bottom line is, I didn't even consider buying this one again, and will not use this one as long as I have a working alternative.