Will catnip hurt dogs?
This is actually one of my favorite herbs, I'm sorry it's not avlable in stores anymore... But I've heard it can be purchased online, just make sure you have enough catnip!
I use it to trn my dogs. They get a little upset when they think a squirrel is around, so when that happens I give them some catnip, then give them a treat and it teaches them to calm down.
I use a special spray, it just gives them a scent.
If you want to avoid possible side effects like diarrhea or vomiting (which I assume would be more common in cats than dogs) then this article has a lot of good info.
Catnip is a potent cat-attractant and has little effect on dogs. Cats, however, may have a tendency to overstimulate, become aggressive or even hyperactive. Overstimulation of cats may cause them to urinate, vomit, defecate and even have seizures. When administering catnip, keep a safe distance from your cat. Avoid touching your cat while it's doing it's business, and be sure to wash your hands after handling catnip, because the essential oil is absorbed through the skin.
I'm pretty sure it's safe for dogs, so long as you don't overstimulate them.
I wouldn't use it as a long-term habit because of the possible adverse effects in cats.
I would use it to trn my dog to follow commands and then when it's a routine thing you can stop the catnip so they don't associate catnip with the command.
I've never used catnip on dogs, but it works well for my cat, so I don't see why it wouldn't work for a dog as well. As @Sammitch states, catnip can stimulate dogs, so you will want to use it in short spurts and in moderation.
But as for whether catnip is safe for dogs, the article @Bruno mentions cites a study that found "No significant effects on dogs' behavior, health, or performance when used in the recommended quantities."
So, in short, catnip can be a good