[Bobby dog]

Dori:
This is from Sentinel’s FAQ section under general FAQs:
I see a few fleas on my dog. Are Sentinel Flavor Tabs working?
You may see an occasional “hitchhiker” adult flea that your dog has picked up at the dog park or in the yard or other infested environments. Since Sentinel Flavor Tabs stop fleas before they become adults, you will need an adulticide, such as CAPSTAR® (nitenpyram) Tablets, to eliminate the occasional adult flea.

http://www.sentinelpet.com/faqs