It stop the fleas from breeding and/or kill flea eggs and larvae in the environment.

They are the exact same product. A vet prescription is only required if you are ordering from a country that requires it. We ship from Singapore which doesn't need one. The products are still genuine though as they are wholesale purchased from the manufacturer in the related country.

Sentinel Flavors are now discontinued and the Sentinel Spectrum is the new brand/packaging for the product.