Red bumps - appear to be flea bites? - on frontline and had Flea Bath

Hello: See photos - I noticed tonight about 15 or more red bumps on Champ's belly - which appear to be flea bites.

Over Christmas, we traveled to my Grandmother's house in Delaware. She has a golden retriever (2.5 years, on flea preventive) and approximately 5 cats- mainly outdoor but also come in and live in the basement. The cats are not on flea preventive and pretty positive they have cat fleas (not sure if difference between dog/cat fleas).

In years past, my other dog Milo, would definitely get fleas while at my Grandmothers- they were easy to spot on him because he was yellow. This year, we put a fresh application of frontline on Champ around December 1st, was at my Grandmothers from December 23-25. When we got back, I paid the $ to have a professional flea bath done at a local pet spa (~ December 28th). On January 1, I applied another application of Frontline plus. I have read some fleas have evolved to not be affected by the active ingredient in Frontline.

I live in Coastal Virginia and it has been pretty mild winter so far - spare the 8 inches of snow we received Friday night/Saturday. Champ did seem to be itching more in the last couple of days - my GF noticed the itching as well. We have not changed food.

I find it odd that today is the first day I am noticing these red spots (if they are indeed from Christmas time), I feel like I would have observed them before on a belly rub but maybe not. Could the recent cold weather "activate" the fleas to latch onto a living host?

The internet gives a plethora of homemade spray remedies to try. I am semi apprehensive on trying these. Not positive it is time to go to the vet.

Thoughts/suggestions/input is appreciated- in addition - i do not see any fleas on Champ and I checked his bedding - do not observe any there either. I washed his bedding tonight to be extra cautious.

https://i.imgur.com/b9hk4wU.jpg
https://i.imgur.com/g1KMPe1.jpg

You could have brought fleas home on your own clothing etc. and they're now in your carpeting and just finding Champ. If that's the case, you'll have to treat the house (we used flea bombs 30 years ago when our first two cats entered our lives carrying hitchhikers)...just washing bedding won't do it, nor will just treating Champ. This is assuming that those really are flea bites...they sure do look like bug bites of one kind or another.

Good luck with figuring it out and killing whatever it is.