A degree of halitosis (oral malodour or foetor oris) is common in healthy people, particularly after sleep. It seems to originate from the mouth, resulting from the metabolic activity of bacteria present in oral plaque. Halitosis at other times is a distressing complaint from which few people probably escape completely and which is still incompletely understood. The true prevalence is not known, but one recent study suggested that nearly half of a group of young women (dental hygienists) believed that they sometimes had halitosis.1

Halitosis generally has as its basis bacterial putrefaction of food debris, cells, saliva, and blood.2 In particular, proteolysis of proteins to peptides, amino acids, and thence substrates with free thiol groups, such as cysteine and reduced glutathione, gives rise to volatile fluids and sulphides.3 Acetone, acetaldehyde, ethanol, propanol, and diacyl are also important causes of …