Pros: The fleas are likely going to die
Cons: Both our cats could have been very sick for a few days.
On the advice of the vet, we treated our 3 month old kittens with "Advantage" as a flea precaution. Both are house cats and only get outside on their harness with supervision.
Within a few days both came down with the following bad reactions:
-loss of appetite
Both cats had to be taken to the vet where fluids had to be administered (due to dehydration). Tests on the blood, x-rays and visits in an attempt to find the cause cost us $500 not to mention the worry of a sick pet.
Both cats coming down with the same symptoms seemed very strange until we read the possible side effects of Advantage. Our cats were fine after a couple of days but our family will never use this product again.