AN IMPORTANT AND GOOD REASON NOT TO MICROCHIP YOUR PETS! C A N C E R!!!!
When we put a microchip into our companion animals we essentially are depositing a foreign material into the body. What happens to something that doesn’t belong? Well we all know the answer to that – just like a splinter for example the body does it’s best to PUSH IT OUT. If it can’t push it out…it tries to wall it off to protect the rest of the body from it…and this is where problems can arise. No major long term studies have been done on microchips and yet the ones that have been done showed that tumors can grow AROUND the chip and surrounding tissue!
In my eyes just not worth it, especially since the only advantage is for lost pets however Pets rarely check anyways.  Yes chances are cancer may never happen but it is not a chance, that I’d take personally…foreign materials do NOT belong in the body…

Dogs Naturally Magazine Article: Microchip your Pets?