When people become ill, they often notice changes in their body’s usual scent. This phenomenon is rooted in biological processes within the body. Illness alters internal chemistry, leading to the production and release of different airborne molecules that our noses can detect. This article explores the scientific reasons behind these shifts in body odor during sickness.
The Biological Basis of Illness-Related Odors
The human body continuously produces and releases volatile organic compounds (VOCs). These airborne molecules are byproducts of normal metabolic processes and contribute to an individual’s unique “odorprint”. When a person falls ill, their internal physiological state changes, which alters the types and concentrations of these VOCs.
Illness often disrupts the body’s normal metabolic pathways, leading to the production of different or increased amounts of certain VOCs. Changes in cellular respiration or tissue breakdown can generate unique chemical signatures released through breath, sweat, and other bodily fluids. The immune system’s response to infection or inflammation also contributes to these odor changes, releasing specific chemicals and inflammatory mediators that can be perceived as distinct smells.
The complex interplay between the body and its resident microorganisms also influences odor production. Skin, gut, and other areas harbor diverse communities of microbes. These microbes metabolize substances secreted by the body, such as sweat components, breaking them down into odorous byproducts. During illness, changes in the natural microbiome or specific infectious agents can lead to novel or altered microbial byproducts, further contributing to a modified body scent.
Specific Illnesses and Their Characteristic Scents
Some illnesses are associated with distinct body odors due to specific metabolic changes or microbial activity. Diabetic ketoacidosis (DKA), a serious complication of diabetes, can cause a sweet, fruity, or acetone-like smell on the breath. This odor arises from the body burning fat for fuel when it cannot use glucose, leading to a buildup of ketones, including acetone, in the blood and expelled through breath. The smell is often described as similar to nail polish remover or pear drops.
Kidney failure can result in an ammonia-like or urine-like smell, sometimes described as bleach-like, on the breath or body. This occurs because the kidneys are unable to filter waste products, such as urea, from the blood effectively, leading to their accumulation and release. Severe liver disease can cause a distinctive musty, sweet, or “fishy” odor, known as fetor hepaticus, on the breath. This smell is linked to the liver’s impaired ability to process certain toxins, specifically sulfur-containing compounds like mercaptans and dimethyl sulfide, which then accumulate and are exhaled.
Specific infections can also lead to characteristic odors. Pseudomonas aeruginosa, a bacterium often involved in hospital-acquired infections, produces a grape-like or tortilla-like aroma, sometimes described as sweet or resembling corn chips. Diphtheria, a serious bacterial infection, can impart a unique sweet or sweet-rotten breath smell, sometimes compared to ripening grapes.
While not typically detectable by the human nose, ongoing research explores unique odor signatures for certain cancers. Cancer cells produce volatile organic compounds (VOCs) that differ from healthy cells, creating a distinct “odorprint”. Although humans cannot generally perceive these subtle changes, trained detection dogs can identify various cancers, including melanoma, lung, and ovarian cancer, from patient samples like breath, urine, or blood.
Beyond the Smell: What It Means and When to Seek Help
While changes in body odor can be indicators, they are not reliable tools for self-diagnosis. Many factors influence body odor, including diet, hygiene practices, medications, stress, and hormonal changes. An unusual smell alone does not definitively indicate a serious illness.
Despite limitations for self-diagnosis, the potential of odor analysis in medical diagnostics is a growing field of research. Scientists are developing advanced technologies, such as “electronic noses” (e-noses), that mimic the mammalian olfactory system to detect and identify disease-specific VOC patterns. These devices are being investigated for non-invasive screening and early detection of various conditions, including cancers and infections.
It is important to consult a healthcare professional if you notice a persistent, unusual, or new body odor, especially if accompanied by other symptoms of illness. Symptoms like fever, fatigue, unexplained weight loss, pain, or changes in thirst or urination, when combined with an unusual odor, warrant medical evaluation. A medical professional can assess symptoms, conduct tests, and provide an appropriate diagnosis and treatment plan.