When brushing or combing is not routine, mats become bigger
and the skin may be pulled almost constantly. It can actually full
the hair out of their skin. Each time a dog gets wet, the mat
tightens more and becomes even more painful for the animal.
Skin can become irritated and ulcerated from the constant pulling.

At Bark Avenue, I have have seen mats so advanced that they
were nearly impossible to cut out with a pair of sharp scissors
because they were so close to the skin. This can result in a
professional groomer to have to totally shave the dog.

Common places that mats accumulate:
Behind ears
Between back legs
Along the back of the haunches
In the groin area
Underneath front legs
Under the collar

Again, pets with larger mats, mats close to the skin, or mats
which cause extreme discomfort should have the mats removed by
a professional groomer.
Removing hair mats is fraught with potential complications.
Mats are often firmly attached to the skin, so you must be
extremely careful not to cut the skin as you cut off the mat.
The best way to avoid cutting your pet's hair is to groom her
frequently and not allow the mats to form.

Even the tiny little fine mats, amounting to no more than five or
ten hairs, can pull the skin under the dog’s arms and can cause
infections from the transfer of bacteria around genital areas. The
coat is much finer on the under belly of our breed, therefore, it
mats much easier.