It is my understanding in Lord of the Rings most folk dismiss athelas, also called kingsfoil, as a useless weed, while it's actually a healing herb. This is probably because by the time of the book's events, they haven't had a king to use it for a long time.
It's not made clear whether kingsfoil only works in the hands of the king of Gondor (or any king for that matter), or if it can be used by any person with less powerful effects. But it is definitely hinted at that it's only truly effective in the hands of a king.
However, in the second Hobbit movie, Tauriel -- an elf and certainly not a queen -- successfully uses kingsfoil to help someone recover from a pretty serious magical wound.
We know Tauriel was invented by Peter Jackson. Did he mess this up, or is this usage of kingsfoil actually supported by the source material?