At some point, almost every person who owns a beautiful Shih Tzu as a pet, will have to decide whether or not to trim the hair on the bridge of their Shih Tzu's little nose and muzzle.
There is a way you can trim the hair over the bridge of the nose, so that the hair does not grow up, into, and onto the face, but it does require a steady hand and very regular trimming. Once you have decided to clip this hair, you are pretty much making a commitment to keep this area trimmed all the time, because it does grow quite quickly and those little hairs can irritate a Shih Tzu's sensitive eye area.

The hair that you want to trim -- so that you still have hair for a topknot -- is just the hair that falls over the stop of the nose. If you put your finger on it and pull the hair down into a moustache on either side, and take the rest up into a topknot, it is the hair on the 'stop' that can be trimmed. Some groomers will use a special clipper to do this.  I recommend having a professional groomer clip it first and then just maintain it yourself after that. The best kind of scissor to use for this are the little ones with the rounded tips on them. I have purchased mine at Petsmart, but they are also available online from places such as Pet Edge and Cherry Brook.

If you would like to keep bows in a topknot, you can still have this even with the nose hair being clipped. It is perfectly fine to have a topknot in your dog's hair every day. It does NOT hurt the dog and, while it looks pretty, its main function is to keep the hair out of the dog's sensitive eye area.  A topknot should be re done daily.  The hair is brushed using a light conditioning spray to keep the hair from breaking, and the topknot itself is not too tight where it pulls the dog's hair or creates discomfort. You will know when your dog's hair is too tight if his/her eyes are more 'open' than usual, if your dog attempts to rub it on the floor or pull it out, and is unable to blink properly.

If you decide to go ahead and trim your dog's nose and not have a daily topknot, you will still have hair flopping into its face with some degree of regularity. The best bet for you is to have your dog given a 'teddy bear' clip so that its face is clear of all hair, but leaving enough to create a tiny topknot on the top of its head, for fun and pleasure.

I am often asked questions about growing out the nose hair after it has been clipped on a Shih Tzu. I have personally done this myself with my Shih Tzu. The process is long, and you have to be able to stand a somewhat messy look to your dog while it is growing out. It took about nine months to a year to completely grow this nose hair back so that it once again fell into the moustache fall nicely. There are products that you can use while growing out the nose hair to smooth the hair down from the eyes, and they must be applied daily. The products that I have used are WELLA CHOLESTEROL creme, and water based gels. Personally, I prefer to just use a little water and comb and fingers to press the hair down. During the growing out period, the hairs may irritate your dogs eyes, and you must check the eyes daily for problems. Your dog's eyes may also water much more while this hair is growing out creating facial staining. I like to use those pre moistened wipes for cleaning puppies on the face, EYE WIPES from Pet Edge to smooth the hair down and to clean the facial area daily.

Whether you decide to clip the hair on the bridge of the nose or not, no decision is final. You can always grow the hair back out if you change your mind. Most professional groomers readily cut the hair on the nose bridge, so if you take your dog to be professionally groomed, and do not want this area clipped, you must communicate this explicitly to the groomer. I personally prefer to leave the nose hair in place as it makes the moustache fall thicker and prettier. Your decision should be based on your preferences and the temperament of the dog.