A tangled undercoat can indicate that a dog is long overdue for a grooming, that the dog has been on a messy outing resulting in massive tangles, or that the dog is going through a seasonal shedding period. Regardless of cause, a thorough grooming session is in order. Put the coat in order, and groom often to prevent risk of problems moving forward.
Attacking the Problem
Depending on the severity of the situation, you may be able to untangle with a good brushing. But if the damage is overwhelming, or if the dog suffers during the brushing, consider using a tangle-removing tool on the tangles and mats or having a professional shave the dog to start a new coat. Do not attempt to shave your dog or to clip out tangles close to the skin.
Brushing Out Tangles
Brush out tangles separately, in sections. Hold the hair at the base of the skin to try to prevent pulling while you attack each tangle. Brush from the tips of the hair first, working toward the skin.
Some tangles are worse than others, so call in a groomer for frustrating ones. Clipping the mats from these areas will allow new hair to grow in, and you can start fresh with brushing and maintenance. Check the areas near the ears, and under the tail and the underbelly, for mats and tangles. If your dog needs a redo, the groomer will use electric clippers to remove most of the coat. Depending on damage, he or she will choose a blade size that leaves a half-inch or more of coat on the dog.