And yes, dogs have allergies. They can also get sick. If anything else is going on, get your dog to the vet. Dogs can also be allergic to their food... But I don't think that would make them sneeze... Just itch.
Take your Schnauzer (not snouzer) to the vet. This has been going on for a month and it still hasn't occurred to you that a vet visit is needed? What are you waiting for?