I've used Sentinel for years with all my dogs and none of them have any sensitivity issues. We've never even had fleas. Jessica, I quoted you because you really should give Ty heart worm preventative all year.Especially since you live in Houston. I hope I don't sound critical or bossy! Like you, I used to give my dogs HW meds only in the winter too, but now I know it was just lucky that they weren't bitten by a mosquito carrying heart worms during that time. It only takes that one bite without the protection of HW meds. In Dallas, we can have mosquitos anytime, so I know for sure you can in Houston. I've just been thru HW treatment with my rescue dog Jack and it's really tough on everyone (especially Jack!). You don't want to risk it! Your vet should have told you that you need to give them all year.
When I took Winnie for her puppy appointments, the vet gave me one small sized Sentinel (based on her weight at the appointment), then the next month at her next appt., she'd give me another one.
Sorry I should have clarified that I only do the flea/bugs during summer. He does get heartworm (Heartguard) all year round - on the 15th of each month

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