I don't know what the scenario is in your county, but here in the UK
the OTC flea products have to be licensed by the VMD (Veterinary
Medecines Directorate) the same people that license the PSL products
available from the Vet, such as Advantage and Front Line.

OTC products therefore have to under go rigorous testing for saftey,
efficacy and overall effectiveness.  That means they must be safe and
effective before they can be sold!

As the products have come from the Veterinary market (a product is
released, pateneted and eventually gets a PSL license.  Three years
afterwhich an OTC or GSL license can be applied for which takes two
years to obtain)I know that it is no more dangerous than the product
supplied by the Vet.....as it is a veterinary medecine!

The reason that we are not allowed to sell Advantage as a GSL product
OTC is simple, it is still in a form of testing.  For the first three
years release the VMD need to know that they can contact the owners of
animals treated with the product.  That is to say the vet keeps
records, whereas this would be impossible for retailers.  After that
(in this case) the manufacturer does not have to apply for a GSL
license, but believe me a carbon copy will be out soon enough.

The scary thing is that I know of a recent survey of vets where dogs
and cats were taken in with 'flea concerns'.  From 500 vets surveyed,
only 73 were competent enough to point out that the home environment
should be treated for fleas as well, therefore preventing
reinfestation.  What is even more worrying is that with the cats over
100 vets suggested immediatley protecting the cat from reinfestation
with sprays and flea collars....all at the same time!  Talk about
trying to put your cat into anotholeptic shock, how dangerous is that!

The OTC market needs the Vets and pharmaceutical companies for sure,
however they also need the OTC companies to make pets more accesible
to owners.

Over here Advantage is going to cost you £35-40, a vet household flea
spray is about £15 and don't forget to worm your pet (fleas being
carriers of worms) £12.  Thats a total of $100 give or take for
exchange rates, now from the OTC market that will cost you $30.

As for safety, follow the instructions on the pack you will be as safe
as at the vet, and it would seem safer than some less scrupilous
establishments.

If however you do have any concerns about your pet's safety and
health, please do not hesitate in finding a **good** vet and taking
your animal there.  Most breeders and pet shops will be able to
recommend the best practice in your area.