The wormer should have already cleared his system, so it shouldn’t have been that, but there are any number of reasons that dogs vomit. After a dog has vomited, they should have no food or water for a few hours, then give about 1 oz of water and see if they keep it down, if so then they can have a little more water about an hour later and then SLOWLY reintroduce food and regular water. If they vomit again after leaving them with no food and water for a few hours, they should see a vet. That’s a sign of a blockage, or other serious condition.
