Dry mouth (xerostomia), is a fairly common, well-researched condition, which is an indirect cause of oral malodour. This systematic literature review looked into another cause of bad breath: adverse drug reactions in the orofacial region causing halitosis. The study focused on extraoral halitosis, and its subdivisions, particularly blood borne halitosis in which malodourous compounds in the blood stream are carried to the lungs, passively diffused across the pulmonary alveolar membrane to enter the breath. An electronic search was conducted in various databases. Inclusion criteria were: editorials, case control studies, retrospective studies and randomized double-blind studies published in English between 1983 and March 2017. The search identified a total of 23 articles. According to these, drug-related halitosis may be caused by nine medications. Dimethyl sulfoxide, cysteamine and suplatast tosilate are metabolised to dimethyl sulfide, a malodourous compound that is stable in blood and is transported into the breath. Disulfiram is reduced to carbon disulfide, also a stable compound in blood. Nitric oxide reacts with foul-smelling volatile organosulfur compounds. The degradation of penicillamine raises the pH level, favouring the growth of gram-negative bacteria in the oral cavity producing halitosis. Chloral hydrate, phenothiazine, and paraldehyde could not be related to halitosis. The analysis showed that halitosis can be caused by medication but does not correlate to any specific disease or specific form of drug therapy. The pharmacological compounds identified as causes of halitosis are administered to treat a broad spectrum of diseases, or in therapeutic regimes.