The short answer
Monthly, for most products. Some, like Bravecto, last 12 weeks. The Seresto collar provides up to 8 months. Whatever the product, consistency matters more than which one you pick. A missed dose is how infestations start.
The major products and their schedules
Monthly oral chews: Simparica, NexGard, and Simparica Trio are given once a month. Simparica Trio also covers heartworm and ticks, which simplifies your parasite prevention to a single monthly dose.
Extended oral chew: Bravecto is given every 12 weeks for flea and tick protection. That’s 4 to 5 doses per year instead of 12. It’s a good fit for owners who struggle with monthly schedules.
Topical (spot-on): Products like Advantage II and Revolution are applied monthly to the skin between the shoulder blades. They work well but can be tricky with thick-coated dogs. Make sure the product reaches the skin, not just the fur.
Collar: Seresto provides flea and tick protection for up to 8 months. One collar, minimal effort. It’s not as targeted as oral products but works well for dogs with consistent wear.
Year-round or seasonal in Ontario?
Ontario’s outdoor flea season runs roughly May through November. After that, freezing temperatures kill outdoor flea populations. So seasonal prevention covers the outdoor risk.
But if fleas got into your home in the fall, they’ll survive indoors all winter in your heated house. Year-round prevention eliminates that risk. It also means you never have to remember when to start and stop.
If you’re using a combo product that covers fleas, ticks, and heartworm, year-round dosing is already the simpler approach. Your vet can advise on the best schedule for your situation.
Why consistency matters
Flea preventives don’t build up in your dog’s system. Each dose provides protection for its labelled duration, then it’s gone. A late or missed monthly dose creates a window where fleas can bite, feed, and start laying eggs. By the time you notice, you’re dealing with an infestation that takes weeks to resolve.
Set a phone reminder. Give the dose on the same date each month (or every 12 weeks for Bravecto). It’s far easier to maintain prevention than to fight an established infestation.
Key takeaways
- Most flea preventives are given monthly. Bravecto lasts 12 weeks. Seresto collar lasts 8 months.
- Year-round prevention is simplest and eliminates the risk of indoor winter infestations.
- Seasonal prevention (May through November) covers outdoor flea risk in Ontario.
- Consistency matters more than product choice. A missed dose can spark an infestation.
- Combo products (Simparica Trio, etc.) cover fleas, ticks, and heartworm in one dose.
References
- Cornell University College of Veterinary Medicine. “Flea and Tick Prevention.” vet.cornell.edu
- AKC. “Best Flea and Tick Prevention for Dogs.” akc.org
- PetMD. “How Long Do Flea and Tick Medications Take to Work on Dogs?” petmd.com
- VCA Animal Hospitals. “Flea Control in Dogs.” vcahospitals.com