My Border Collie has extremely thick, long hair and when we first got him it was a pleasure to brush his coat and keep him looking shiny. However, the moulting and hair loss has become a real problem; I have to hoover the sofas and chairs everyday unless we want his hair on our clothes! My vet said to keep up with regular grooming but I really felt it was getting worse so I needed to go one step further.
I also noticed that his skin underneath was quite dry and it looked like he had dog dandruff (it stood out a lot against his black hair) in some places. I searched online for skin problems in dogs and also dog moulting problems and I found some useful advice.
Apparently, what causes a lot of excessive moulting in dogs is modern central heating and the 'fake' temperature environments we have in our homes compared to outside. I would have to agree that we noticed his moulting a few weeks into the winter when we had been having our heating on a lot (nearly all day sometimes). The natural chemical signals in a dog's body that tell it to either grow hair or shed it get confused at this time of year; they spend a lot of time in a warm/hot home and then go outside to extreme cold temperatures.
So what happens is a constant change in growing extra hair and shedding of hair, which at the time seemed excessive and quite worrying. I learned that as well as grooming and skin treatments it is the dog's diet which really makes a difference to solving these problems.
There are many dog food supplements you can buy which contain oils such as omega 3 and 6 and nutrients that condition their skin and hair follicles. I noticed a huge difference in his coat after this, the dandruff was gone and although he moulted it was regular hair loss, not excessive or constant.