Not all flea and tick medications are created equal – in fact, it has been proven over and over that there are some chemicals in some flea and tick medications that can have devastating results for your beloved pet.
Heartworm is spread through mosquitos. If you live in a hot, humid climate, then you need to give your dog heartworm year round. If you are going to start treating them for heartworm, make sure you test your dog first – if you give them medication and they have heartworm, they can get very sick and even die. The safest heart worm medication is Interceptor. If you want to add the flea/tick then it is a product called Sentinel
If you wanted to just do Flea/Tick medications, I recommend the plain Revolution.
You should not need to give these products year round in the Seattle area, but perhaps over the warmer months.
Please, please, please, do not EVER give your dogs products with afoxolaner in it – Nexguard, Bravecto, Simparica, Comfortis, Vectra 3D, Credelio – these have all had deaths and seizures reported after administration.