There are two types of mouthwash: Cosmetic and therapeutic.

Cosmetic mouthwash may temporarily control bad breath and leave behind a pleasant taste, but have no chemical or biological application beyond their temporary benefit.  For example, if a product doesn’t kill bacteria associated with bad breath, then its benefit is considered to be solely cosmetic.  Therapeutic mouthwash, by contrast, has active ingredients intended to help control or reduce conditions like bad breath, gingivitis, plaque, and tooth decay.

Active ingredients that may be used in therapeutic mouthwash include:

· Cetylpyridinium chloride;

· Chlorhexidine;

· Essential oils;

· Fluoride;

· Peroxide.

Cetylpyridinium chloride may be added to reduce bad breath.³  Both chlorhexidine and essential oils can be used to help control plaque and gingivitis.^{4, 5} Fluoride is a proven agent in helping to prevent decay.⁶ Peroxide is present in several whitening mouthwashes. Therapeutic mouthwash is available both over-the-counter and by prescription, depending on the formulation.  For example, mouthwashes containing essential oils are available in stores, while those containing chlorhexidine are available only by prescription.

Transferred from http://www.ada.org/en/member-center/oral-health-topics/mouthrinse