Will Falconer, DVM Moderator
Hi Janet,
It's generally a mistake to give "anti-" drugs when an animal is fighting disease. Benadryl is antihistamine. Is his congestion wrong, and needs to be countered? No, it's part of his "fight," part of Nature's way of battling this virus, just like sneezing or a fever.
The trick is to not get caught up in how you feel about him, but focus instead on how he's doing. Still eating? He's not very sick. Still active? Ditto.
He'll get better faster if you don't intercede with drugs. If you want to hasten recovery and support his fight, get a vet homeopath on board and list off symptoms to him/her. Then, a remedy can be found that helps quicken recovery. My Resources page has the AVH list there, that list vet homeopaths by geographical region as well as percentage of their practice that is homeopathy.