Chemotherapy’s effects often extend beyond cancer cells, causing noticeable changes in a patient’s body odor and altering their perception of smells. These sensory disturbances are frequently reported side effects, affecting many individuals undergoing treatment. The changes result directly from how the body processes and eliminates the potent chemotherapy drugs, leading to temporary but disruptive effects.
Changes in Body and Breath Odor
Patients and those close to them often report a distinct, unpleasant odor emanating from the skin, breath, and bodily fluids. These external odors are a consequence of the body attempting to excrete the chemotherapy agents and their breakdown products. The smells are commonly described as metallic, chemical, or sometimes even sickly sweet or foul, often saturating sweat, urine, and even bed linens.
The characteristic metallic or chemical smell is attributed to volatile organic compounds released through the skin and lungs. These compounds are the metabolites, or breakdown products, of the chemotherapy drugs. For instance, when certain metals, such as ferrous iron present in the body, react with human skin cells, they produce odorous compounds that result in a metallic scent.
This temporary change in personal scent is not a reflection of poor hygiene or a worsening medical condition. Instead, it signals that the drug is actively being metabolized and cleared from the system. The intensity of the odor often peaks shortly after an infusion when the drug concentration is highest and tends to diminish as the body processes and eliminates the compounds.
Alterations in the Sense of Smell
In addition to changes in external odor, chemotherapy can profoundly alter the patient’s internal experience of smell, making previously neutral or pleasant aromas seem repulsive. These changes in olfactory perception can be categorized into two main types of distortion.
The first is dysosmia, which is a qualitative distortion where a familiar smell is perceived incorrectly, such as when a favorite food smells rancid or heavily chemical. A second type of alteration is phantosmia, where the patient perceives an odor that is not actually present in the environment. Patients often report smelling phantom odors that are metallic, burnt, or chemical in nature. The prevalence of smell alterations has been reported to occur in a range of 5% to 60% of patients receiving chemotherapy.
These olfactory changes can have a severe impact on food intake and overall nutrition. When smells are distorted or intensified, it often leads to a strong food aversion, decreased appetite, and potential weight loss. The sense of smell works closely with the sense of taste, and disruptions to one can make food bland, bitter, or entirely unappetizing, complicating the process of maintaining adequate nutrition during treatment.
Understanding the Biological Mechanisms
The physiological reasons behind these sensory changes are complex, stemming from chemotherapy’s mechanism of action on rapidly dividing cells. The external body and breath odor are primarily a result of the drug’s metabolic pathway. Chemotherapy drugs are processed by the liver through hepatic metabolism, breaking them down into inactive metabolites.
These metabolites, which are often volatile, must then be excreted by the body, typically through the renal system (urine) and the skin (sweat and breath). The odor arises as these volatile compounds are released, sometimes reacting with the skin’s surface to produce a noticeable scent. This process is temporary and coincides with the active clearing of the drug from the body.
The alterations in smell perception, such as dysosmia and phantosmia, are linked to the drug’s effect on specialized sensory cells. The olfactory sensory neurons, located in the nasal passages, are known for their high turnover rate. Since chemotherapy drugs target all rapidly dividing cells, these olfactory neurons can be damaged or their renewal cycle can be disrupted. This damage to the olfactory epithelium can lead to misfiring signals, causing distorted or phantom perceptions of smell. Furthermore, some chemotherapy drugs are known to have neurotoxic effects, which can directly impact the nerve pathways leading to the olfactory bulb and brain.
Practical Management and Coping Strategies
Managing the changes in body odor and smell perception requires a proactive approach focused on minimizing discomfort and maintaining nutrition. To handle the external body odors, frequent and gentle hygiene is helpful, including showering regularly with mild, unscented soap. Changing clothes and bed linens often can also help prevent the accumulation of odorous drug metabolites.
Staying well-hydrated is another helpful strategy, as drinking plenty of fluids helps the kidneys process and flush the chemotherapy metabolites more efficiently. For managing the distorted sense of smell, serving food cold or at room temperature can reduce the release of volatile odors, making meals more tolerable. Strong aromas are often more offensive, so avoiding foods with powerful smells, such as certain meats or strong spices, can limit nausea.
Using plastic utensils instead of metal can help mitigate the common metallic taste that often accompanies these sensory changes. Patients should also consider consulting with a registered dietitian who can help create a nutritionally sound diet plan. Discuss all sensory changes with the oncology team, as they can rule out other causes and offer further guidance.