I have an 11 year old female cat who eats toilet paper and kleenex if I ever leave it out. She does this even if she has  food in her dish and has done it all her life.  Her diet is Science Diet with a little Fancy Feast as a treat.  She definitely eats it and not just plays with the tissue.  I assume with the Science Diet she is getting balanced dietary requirements. This behavior is not linked to a reaction to me.  Any ideas of why she does this?