The best meds I have found/used and find to be the most effective on our dogs is Bravecto. It is a chewable & lasts for 3 months. Here's why I prefer it to other brands & delivery methods:
1- At appx. $52, that's $17 a month for flea/tick prevention & it REALLY WORKS!
2- My Vizsla has severe hair loss from any topical meds or flea collar, so this just makes sense
3- My Vizsla doesn't get fleas/ticks nearly as bad as our other dogs (maybe due to his coat?!?), & this med is great because it seems to last longer than 3 months for us. I like to LIMIT the amount of chemicals I put in his little body & if I can give this every 3-5 months instead of giving him something monthly or topically, I am ALL for it!!
**BE AWARE, this might NOT be fleas. This could be an allergy (food, weather change, chemical, etc), eczema, stress, or many other things. I have a 3.5 yr old Aussie that has SEVERE skin allergies & the tiniest change in her environment can set her skin off into a war zone of itching, inflammation, redness & open sores. She is allergic to several foods (eggs, most grains, potatoes, apples, etc), allergic to chemicals in most dog shampoos (fragrances), allergic to flea bites, and the list goes on!!! Really, if she gets bitten by a few fleas- forget about it; she honestly breaks out in hives & her skin gets a yellow, hard crust all over it, then bleeds & bleeds! Its taken us many years & many, many thousands of dollars to figure out what triggered the problems. Now that we know what we are dealing with, we can manage it & don't have flare ups, but Bravecto has been a SAVIOR for her, too. If I don't keep up with her Bravecto regularly & she gets a few fleas- she is miserable & I feel like the most terrible person. Oh, & fyi, we had to figure out a LOT of the allergies ourselves. The vet knew something was causing it, but didn't know what. A lot of what we know now was trial & error. We eliminated ALL table scraps & I started using a grain-free dog food. We have always supplemented our dry dog food with veggies, fruit & sometimes other proteins because we think dry dog food is junk- even the best of the best. (*That's our opinion & we don't claim to be correct or experts). In supplementing her food with things, we basically did the elimination diet to see what she could & couldn't handle. It took time, but now we know. We only offer pure, dehydrated meat jerky as treats to eliminate any allergies there.
I know that was a lot. Hope that helped a bit. I just don't know if you are actually dealing with fleas- you should be able to see them if you are.
If you're not seeing fleas, and flea dander, on him, It's going to be something else.
My first thought would be his bedding. Is it a natural material, or a synthetic material?
Synthetic materals can cause fits with Vizslas. The single coat of hair, and very little natural oil, doesn't give them the protective layer other breeds have.