Some species of ticks can carry potentially fatal diseases that are transmitted when they bite your dog, and now is the time of year when some of them are most.
Search your dog for ticks. You should check your canine friend for ticks whenever he has been somewhere that is known to have ticks (hiking.
I have Lyme Disease. My dog does not. Our vet thought this was odd, because dogs spend much more time closer to the ground and inevitably get a lot more tick.