Evaluation of Sour Smell Not Attributed to Body Odor
A sour smell that is not typical body odor most likely originates from metabolic or systemic disease, and requires evaluation for underlying pathology including diabetic ketoacidosis, hepatic dysfunction, or respiratory infection before considering benign causes.
Differential Diagnosis by Odor Quality
The quality of the sour smell provides critical diagnostic information:
- Fruity or sweet-sour odor suggests diabetic ketoacidosis, where acetone and other ketone bodies are exhaled through the breath and excreted through skin 1, 2
- Ammonia-like or urine-like sour smell indicates hepatic failure or uremia, where metabolic waste products accumulate and are released as volatile organic compounds 1, 2
- Foul sour odor may reflect respiratory tract infection with purulent sputum production, particularly in older adults 1
Systematic Evaluation Algorithm
Step 1: Determine the Source Location
- Oral cavity examination should assess for gingivitis, periodontal disease, or dental abscess, which can produce sour-smelling halitosis distinct from typical body odor 3, 1
- Nasal endoscopy may be warranted if the patient reports the smell as coming from the nasal passages, to evaluate for chronic rhinosinusitis or sinonasal pathology 4
- Skin examination should identify any dermatologic conditions that alter sebaceous gland function or create abnormal volatile organic compound production 5, 6
Step 2: Assess for Systemic Disease
- Blood glucose and urinalysis are essential to rule out diabetic ketoacidosis, particularly if the sour smell has a fruity quality 1
- Liver function tests should be obtained if hepatic dysfunction is suspected based on other clinical features 1
- Chest examination and imaging may be indicated if respiratory infection is suspected as the source 1
Step 3: Consider Metabolic and Genetic Disorders
- Certain genetic disorders and metabolic diseases produce characteristic body odors through accumulation of specific volatile organic compounds that can present as sour or unusual smells 5, 2
- Trimethylaminuria and other disorders of amino acid metabolism can produce distinctive odors that patients may describe as sour 2
Critical Pitfalls to Avoid
- Do not dismiss the complaint as purely hygienic or psychogenic without first excluding serious systemic disease, as sour body odor can be an early sign of diabetic ketoacidosis, hepatic failure, or other life-threatening conditions 1, 2
- Do not assume all unusual odors are body odor-related when they may actually represent halitosis from oral or respiratory sources requiring different management 3, 1
- Do not overlook the possibility of phantosmia (olfactory hallucination) if no objective odor can be detected by others, which requires neurological evaluation and brain MRI 4, 7
When Imaging Is Indicated
- MRI brain with contrast is appropriate if the patient is experiencing an olfactory disturbance (smelling something that others cannot detect) rather than producing an actual odor, to evaluate for structural lesions affecting the olfactory pathway 4, 7
- CT maxillofacial without contrast is indicated if sinonasal inflammatory disease is suspected as contributing to altered smell perception or production 4
Management Based on Etiology
- Oral sources require referral to dentistry for definitive treatment of periodontal disease or dental pathology 3, 1
- Systemic disease requires treatment of the underlying metabolic or infectious condition causing the abnormal volatile organic compound production 1, 2
- Nutritional deficiencies (particularly B12, iron, zinc) should be corrected if present, as these can contribute to altered body chemistry and odor production 7