Just a note for thought.
 
If the paint that is used inside the box is of exterior grade, it likely
contains fungicides.  Some years back (not too many - 15 +/- ?!) mercuric
acetate was often used.  If this can (?) be spread to the propolis, wax and
honey - we all know the rest of the story.  I don't know what is commonly
used now or if it would present a problem.
 
Dave P / NJ