And, I agree it's a risk reward thing.
Had three dogs now have tick illness. One was just very lame on her front leg, lethargic and off, she had Lyme and doxy fixed her up pretty quick. She was young and was on Advantix, but it didn't work well enough anymore so I switched to Bravecto at the time.
One was just lethargic overall, he had heart arrythmia at the vet, rushed to the vet teaching hospital, was on doxy and pred together and then doxy. He could have died. He did die a year later of seizures... and kidney failure. He was 11 but I still kick myself for going with the "all natural" tick stuff because the Lyme may have been what killed him.
And still another had RMSF, she had neurological issues- nystagmus, loss of balance. Vet was a good one and recommended doxy first rather than advanced diagnostics, even though the titer was inconclusive. After a few weeks, she was almost back to normal, but had a head tilt for about a year.
So, yeah, I will take the small risk of tick preventatives over all that...
And based on what I've read so far, I'm switching to Simpartica.