sores on cats tail

Question
HI.  I HAVE A CAT THAT IS 15 YEARS OLD.  ABOUT A MONTH AGO I NOTICED THAT SHE STARTED SWISHING HER TAIL BACK AND FORTH AND STARTED HISSING AND BLOWING AT NOTHING.  WHEN I LOOKED HER OVER I NOTICED THAT SHE HAD SOME SORES UP AND DOWN HER TAIL.  SHE IS AN INDOOR CAT, NEVER BEEN OUTSIDE AND SHE DOESN'T HAVE ANY FLEAS AT ALL.  COULD YOU HELP ME WITH WHAT MIGHT BE WRONG WITH HER AND WHAT TO DO TO TREAT IT?  ALSO SHE HAS STARTED USING THE BATHROOM IN THE HOUSE.   SHE STILL USES THE LITTER BOX, BUT SOMETIMES ITS LIKE SHE FORGETS WHERE IT IS AND JUST STOPS WHEREVER SHE IS AND DOES HER BUSINESS.  I KEEP THE LITTER BOX CLEAN.  DO YOU HAVE ANY IDEAS ON THIS ONE ALSO.  THANK YOU FOR ANY HELP.

Answer
It's possible that she has a urinary tract infection.  Often cats who have one will use the bathroom outside the litter box as well as over groom themselves on their bellies and genital area.  If she's doing that it could account for the sores on her tail, or she could have allergies.  I would take her to your vet for a check up so they can run some tests and find out exactly what's wrong with her and hopefully make her feel better.

Amanda