We used to treat our dogs with the liquid stuff that you dot around their necks. Both really hated it and seemed unhappy for the next few days. Over lockdown, with our remaining dog unable to visit anyone else's house and no one visiting ours we left off the flea treatment and all was fine. Now he's picked them up from somewhere. Only a couple and very little flea dirt, so we've caught it early.
What do you use? I'd prefer something we can obtain over the counter and preferably something that the dogs don't feel has poisoned them.