Premature graying refers to a disorder in which your dog's coat begins to lose the richness of its natural color and adopts a dull gray tone. Often this is associated with loss of hair, or the softening of hair which can ruin the texture of a coat in some breeds such as the Schnauzer or others with a typically coarse and wiry coat. Although almost all breeds will eventually lose some of their color and begin to go gray, graying is considered a problem when it occurs much earlier than could naturally be anticipated.
The disease can affect any breed of dog, but studies have indicated that it is most likely to affect dogs that are both small and possess a tightly woven coat as their standard, again making the miniature Schnauzer a prime candidate. It's not necessarily a harmful disease as it causes no real detriments to a dog's overall health, but it can still be very problematic for some people who paid a lot of money for a dog of a certain color, especially if they had plans to put that dog into the show ring. Although not all breeds are marked down for premature graying, most are, and in any case, it's not something that's highly prized among show dogs.
There's no real cure to premature graying, but the key to keeping it in check seems to be spotting it early. By knowing what to be on the lookout for, you can begin preventative and potentially restorative measures while they still have the most chance of being effective. The earliest sign of premature graying is that your dog's hair will begin to get lighter in color near the root, and the hair shaft itself will begin to thin out. This might be hard to notice on a dog with a light colored coat, or on a coat that is normally straight, but it should be very easy to recognize on dark color, and in coats that are normally very coarse. Ironically, show dogs might be at the most risk for premature graying because of the constant stripping and shaping that their coats go through to get them ready for display. As such, if you're the owner of a show dog, you must take great care to be on the lookout for these warning signs.
Once you've noticed that premature graying is becoming a potential problem in your dog, you should take steps to make certain that you're using the proper grooming regiment for your breed. It's very likely that there are specialized shampoos you can buy to help maintain a natural balance of oils and shine to your dog's coat, which can create the appearance of a richer color even after it does begin to fade. The use of a grooming stone (a rough stone much like a pumice stone) can be used to strip out dead hairs (which tend to be lighter) so that the remaining hairs appear darker due to less visual interference.
Ultimately, it's important to remember that there's no real cure for premature graying and past a certain point, you're just going to have to deal with what you've been given. Beware the use of topical medications or dyes as these can cause significant pH imbalances in your dog's skin that could lead to much more serious dermatological conditions.