Raspy voice cat

I have two cats that are sisters. The one gets a raspy voice off and on, I have taken her to the vet a few times for it and all they do is give her antibiotics and it clears up after a day or two. The last time this happened it cleared up on its own but now she is raspy again and has been for about a weeek. She is otherwise normal, eats drinks plays. Doesn't have any discharge from nose or eyes and is not sneezing. I would hate to waste the money again at the vet but I feel so bad for her! Could use some advice please!

Whenever you have taken her in and the Vets have given her antibiotics, what did they say was wrong that she needed the antibiotics?  Since this seems to be happening over and over, I would ask the Vet WHY and exactly what it is.  Do they even examine her or just give her the antibiotics? 

I don't have any idea what it is, but since it cleared up on it's own last time, i would wait a day or two to see if it clears up again, but still call the Vet and tell them it keeps happening and try to get some answers (without taking her in)

They have mentioned heroes zoster since it keeps coming back. They examine her a little but just the basic stuff. My friend works at an emergency vet and says if she seems fine it might just be her or it might be allergies. I just feel so bad because sometimes she sounds fine and other times she sounds terrible. Thank you for responding!

For Herpes Zoster, people usually keep their cats on a low dose of L-Lysine....250mg twice a day.  Have you tried doing this?  It might help.  L-Lysine comes in many different form...powder you can mix in food, paste, chews.  There are many threads on it   Here's just one:  http://www.thecatsite.com/t/303777/most-palatable-l-lysine-supplement