oh! thanks for posting website! i will check it out! never heard of microchips causing uri symtoms but then i never heard of hairballs causing sneezing! Learning a lot from this thread! (or not?) I will read site as I know zero about chips- none of my cats go out or care to go out (even ferals, esp. ferals! seem content to stay within confines of the walls!) Never the less, is good to get them. Thanks again!