If you want to prevent fleas, unless your dog has had an allergic reaction, you need the flea medication provided by the vets. The products sold at Pet Stores aren’t as effective and some have been linked to serious health issues.
A few words of caution though….we’ve received a couple of reports over the years of reactions to even the flea products from the vet’s office. My opinion is based on previous reports of our doodles having issues. First, you should always keep the dosage within your dog’s weight range. For instance, if your dog is 53lbs and the dose range is 35-55lbs – stick with that, do not jump up in weight class. Second, for the first application of a medication apply a tiny amount as a test. Wait eight hours, if the site doesn’t show a reaction then proceed with the entire application.
Visit Pets for Oz for great prices on flea, tick, and heartworm prevention products, no prescription required. They sell the same medications that your vet does.