Hi, I don't know if they are Ok for dogs, but they can be deadly to birds.... Obviously birds are a lot smaller, but I myself find that this type of air freshener irritates my 'chest'. There was a thing on 'How clean is your house' where they showed you how to make a natural freshener....
Bicarb [about 4 tbs]...add a few drops of essential oils [they used tea tree and lemon] wrap it in a muslin cloth and suspend it above the dogs bed. I haven't tried it myself, but it might be worth a go.
Lisa x