Dog allergy is less common than cat allergy. And, contrary to popular belief, dog hair is not what makes you feel miserable - just like with cats, it is their dander that gets to you. For some allergy sufferers, a dog's lick may also set off an allergic response.
Because dogs tend to scratch themselves more than cats, dog allergen can be more easily introduced into the air. The reason for excessive scratching may be that the dog itself is allergic to something in your home. There are hundreds of possible causes of this, the most common is mold. It is worth mentioning that the same source may be worsening your own allergy symptoms, so taking care of it would make life easier for both you and your pet.