crunmbling brickwork in fireplace

[fayemichelle]

we have a woodburner in a fireplace in our dining room. we have lived here for 3 years and have started to notice that the brickwork is crumbling (especially inbetweeb the bricks) in some areas. is this due to damp? and what do have to do to restore it to it's former glory? there is also white powdery stuff in some areas. and finally, what sort of tradesperson would do this (if we can't do it ourselves!)?. thanks in advance:)