Hello, thanks for your question today! I am Dr. Drew, and I am a licensed veterinarian. I'll be happy to help you in any way I can.
It's difficult to precisely describe the possible adverse reactions, without knowing exactly what products were used, but in general, it's not unusual to see dogs become a bit lethargic for 24 hours or so after application of flea/tick products, and many will be restless, or seeming to be "uncomfortable in their own skin", constantly pacing and looking for relief.
If this behavior
is problematic, a degreasing soap such as Dawn dish soap can be used to remove a good portion of the residue that may be causing the discomfort.
It is very rare for any serious effects to occur from one of these products, assuming high-quality veterinary products are used (rather than the grocery store types).
If there's no improvement within 24 hours, then I'd definitely recommend a veterinary examination. As long as Hootie is eating and drinking, even in small amounts, this is not likely to become a major problem.