• Confirm that halitosis is present by smelling the person's exhaled breath.
• Be aware that:
• The person's own assessment is the least reliable measurement.
• The odour can vary with time and be influenced by other factors such as diet, hunger, and oral hygiene.
• Consider repeating the assessment on two or three different days if no malodour is detected on the initial examination.
• Consider feedback from the person's partner or family members.

These recommendations are based on published narrative reviews on halitosis or oral malodour [Rosenberg, 1996; Coventry et al, 2000; Yaegaki and Coil, 2000; Morita and Wang, 2001; Messadi and Younai, 2003; Scully and Felix, 2005a; Porter and Scully, 2006; Lee et al, 2007; Hughes and McNab, 2008; Scully and Greenman, 2008].

• Smelling the person's breath is recommended to confirm halitosis and to exclude suspected pseudo-halitosis or halitophobia.
• It is generally recognized that individual assessment is a poor measure of halitosis [Hughes and McNab, 2008; Scully and Greenman, 2008].
• Because of the difficulty inherent in smelling one's own breath, some people may have exaggerated concerns about their own breath [Rosenberg, 1996; Eli et al, 2001].
• In a study involving 2000 consecutive people visiting a Dutch multidisciplinary breath odour clinic, 15.7% had no objective signs of malodour and were grouped as pseudo-halitosis/halitophobia [Quirynen et al, 2009].
• Subjective (organoleptic) assessment is regarded as the most simple, reliable, and practical method for evaluating the severity of halitosis [Yaegaki and Coil, 2000; Porter and Scully, 2006; Scully and Greenman, 2008; Vandekerckhove et al, 2009].
• Methods such as gas chromatography or measurement of volatile sulphur compounds are more objective and are commonly used in research. However, these methods are impractical, expensive, and unavailable in primary care. The limitations of volatile sulphur compound measurement is discussed in Supporting evidence.

• Enquire about:
• The person's own perception of the problem — including the impact on their quality of life (education, work, and social activities).
• Severity, timing, and duration of the halitosis — for example breath odour upon waking (morning breath) is normal and transient.
• Possible trigger factors — for example certain foods and drinks (including alcohol) and smoking.
• Treatments used to manage halitosis — for example oral hygiene measures.
• Examine the oral cavity to look for oral causes of halitosis including:
• Oral infections — for example oral candidiasis and herpetic gingivostomatitis (see the CKS topics on Candida - oral and Herpes simplex - oral).
• Dental and gum diseases — for example dental abscess or decay, periodontitis, and acute necrotizing ulcerative gingivitis (see the CKS topics on Dental abscess and Gingivitis and periodontitis).
• Suspected cancer — see Referral.
• Dry mouth — which can lead to decreased taste sensation and difficulty in swallowing.
• Problems with dentures — including denture hygiene.
• Tongue coating.
• Review oral hygiene measures — poor oral hygiene is a common cause of halitosis. Ask about:
• Methods used (for example brushing, flossing, use of mouthwashes).
• Frequency of brushing and inter-dental cleaning (for example flossing).
• Denture hygiene — for example whether the person takes their dentures out at night and if they clean their dentures regularly.
• Frequency of dental visits.
• Consider tongue coating as a source of halitosis — particularly in people with good dental hygiene and oral health.
• The posterior region of the tongue is a main source of oral-related halitosis.
• Consider gently but thoroughly scraping the area (for example with a clean plastic spoon or proprietary tongue scraper or tongue brush). The odour from the scraping (which is often yellow in colour) is generally similar to overall mouth odour.
• Review the person's medical history and consider non-oral causes of halitosis. Certain conditions will produce distinctive odours.
• Consider asking the person to breathe out of their mouth (pinching the nose) and then to breathe out of their nose (with the mouth closed). The condition is likely to be:
• Oral or pharyngeal in origin — if odour is detected from the mouth but not from the nose.
• Nasal in origin or from the sinus — if odour is detected from the nose but not from the mouth.
• Systemic in origin — if odour from the nose and mouth are of equal intensity (generally rare).
• Review the person's medication history for drugs known, or suspected, to cause or contribute to halitosis (uncommon).

These recommendations are extrapolated from published narrative reviews on halitosis or oral malodour [Rosenberg, 1996; Coventry et al, 2000; Messadi and Younai, 2003; Scully and Felix, 2005a; Porter and Scully, 2006; Lee et al, 2007; Hughes and McNab, 2008; Scully and Greenman, 2008].

Examination of oral cavity and assessment of oral hygiene

• The recommendations to examine the oral cavity for oral and dental disease and to review dental hygiene are in line with published expert opinion and reflect the fact that in 80–90% of people with persistent halitosis there is a problem in the mouth.
• In a study involving 2000 consecutive people visiting a Dutch multidisciplinary breath odour clinic, an oral cause was found in 76% of people — with the main causes being tongue coating (43%), gingivitis/periodontitis (11%), or a combination of the two (18%) [Quirynen et al, 2009]. Xerostomia was responsible for 2.5% of cases. Only around 2% had an extra-oral cause, no cause was found in 0.8%, and 16% were classified as pseudo-halitosis/halitophobia.
• The recommendation on how to assess tongue coating is based on expert opinion [Rosenberg, 1996; Messadi and Younai, 2003].

Assessment of non-oral causes of halitosis

• The recommendation to assess exhaled air from the nose and mouth separately is based on published narrative reviews [Rosenberg, 1996; Messadi and Younai, 2003; Porter and Scully, 2006; Lee et al, 2007; Scully and Greenman, 2008].