Some groomers experience difficulty when handling aggressive dogs. Often, this is because, although they have been trained to trim, they haven't necessarily had sufficient training with dogs to understand fully why they act, or react, the way they do. A dog's background and past experiences can contribute to its behavior, and some dogs who have been mistreated or misunderstood will be difficult to trim for four or five visits to a well-trained groomer. Then, they become angels. Dog's bite through self defence and because they are worried or scared and feel vulnerable. Act confidently, treating the dog with respect and kindness at all times. If a dog is nervous, talk to him to reassure him. Most dogs are far more ready to please you than children are. Handling the dog with patience, care and understanding is crucial to avoid causing them to react defensively. The secret of success is to put the dog's welfare above the finish of the trim.