Hi I have a little chihuahua pomeranian cross, 17 years old, and he suffering a bit from fleas. I have put an Activyl Spot-On on him 48 hours ago. There doesn't seem to be a lot lot of difference in the decrease of fleas and his scratching. Can I safely use a 7 day natural based flea rinse on him or just wait it out and use a flea tablet. Other than the current flea problem he is quite happy and healthy. I don't want to accidentally overdose him of flea product. Thanks for any adice.