It is probably the most widely used 'antibacterial' and 'antifungal' mouthwash and my personal favourite. It is, in my humble opinion without doubt the best mouthwash for controlling plaque and gingivitis. Because it is anti-plaque it can (if used regularly), help to reduce dental caries but long term use is not advised- see below.
Rinse for 1-minute morning and night for 1-2 weeks- the taste is pretty potent and hangs around for a while, so keep in mind the good it is doing you. It is best not to rinse straight before, or after brushing- in fact, rinse away
from brushing altogether if you can, because it is made slightly less effective by the ingredients in toothpaste.
It is only recommended for short-term use because of its effect on taste and the fact that using it for months at a time will cause some reversible brown staining to build up on your teeth (don't worry your dentist can easily polish this off and if just used for a week or so, this won't happen). One other potential side effect of long term use is the swelling of your parotid salivary gland- a swelling which again is reversible if it happens but is relatively rare.
It is available in most supermarkets such as Coles or Woollies (in Australia) and certainly in chemists. In the UK, a prescription from your dentist is required.
If your gums are too sore to even brush, it can be a very useful substitute, especially following gum surgery, when it hurts to try and brush or if you have an acute painful condition such as ANUG
To have more than just a fleeting effect, a mouthwash must hang around in the mouth and Chlorhexidine is one of the only available mouthwashes currently able to do this. It has a positive charge which means it sticks to negative proteins on tooth surfaces, gums and in your saliva; gradually seeping out over time.
Its benefits can greatly outweigh its side effects in patients who have difficulty cleaning, such as those who are handicapped or suffer xerostomia.