Do we have the ability to smell cancer?

Article by MSc. Mai Viễn Phương, MD - Head of the Gastrointestinal Endoscopy Unit - Department of Outpatient and Internal Medicine - Vinmec Central Park International General Hospital.

Everyone has a unique body odor (BO), which can be pleasant or faint, but when we think of body odor, we often think of an unpleasant smell. Changes in body odor can be caused by puberty, excessive sweating, or poor hygiene. Sudden changes are often triggered by the environment, medications, or the food you eat. However, body odor, especially sudden and persistent changes to your normal scent, can sometimes be a sign of an underlying health condition.

1. Signs of Sudden Changes in Body Odor

 Sudden changes in body odor usually occur in a specific area of the body. Common areas include:

•    Genital area
•    Armpits
•    Feet
•    Mouth and throat
•    Belly button

You may also notice a sudden odor from stool, urine, earwax, or discharge from the genital area. Regardless of the location, the smell can vary. It could be foul, pungent, fishy, sour, bitter, or even sweet. Other symptoms you experience will depend on the cause. If the odor change is due to an infection, it may also be accompanied by:

•    Redness
•    Rash
•    Itching
•    Discharge, leaking, or discoloration

2. Does cancer produce a bad smell?

 When diagnosed with cancer, early detection can save lives. This is why researchers around the world are working to find new methods to detect cancer before it has the chance to spread.
An interesting area of research involves the smells associated with cancer that the human nose may not necessarily detect. Researchers are looking for clues, hoping to harness the exceptional olfactory ability to detect the disease.
In a 2008 study, researchers trained a dog to differentiate between types and stages of ovarian tumors and healthy samples. In controlled experiments, the researchers found that their trained dogs were highly reliable in detecting ovarian cancer. However, they did not believe dogs could be used in clinical practice. They noted that many factors could interfere with the task and affect accuracy.

A 2010 study using dogs discovered that cancer has a specific odor. The cause of this smell is unclear, but it may be related to polyamines. Polyamines are molecules associated with cell growth, proliferation, and differentiation. Cancer increases the levels of polyamines, and they have a distinct smell. The researchers in this study also discovered that cancer-targeted chemicals could circulate throughout the body. They hope to use this knowledge for early detection of colorectal cancer.

Using electronic noses, researchers have been able to detect prostate cancer from the scent patterns of urine. These studies, along with others like them, represent a promising area of cancer research. However, it is still in its early stages. At this point, scent is not a reliable cancer screening tool.

3. Can people smell certain types of cancer?

People cannot smell cancer itself, but you may be able to smell some symptoms associated with cancer.
One example is a tumor that is ulcerating. Ulcerating tumors are very rare. If you have one, it is likely to have an unpleasant odor. The bad smell may be the result of dead or necrotic tissue or bacteria in the wound.
If you notice a foul smell coming from an ulcerating tumor, see a doctor. A course of antibiotics may help clear it up. They may also need to remove dead tissue from the area. It is important to keep the area as clean as possible—moist but not wet.

3.1 Can cancer treatments cause odor?

Dogs can detect certain smells associated with cancer, but humans can also detect some odors.

Typically, these smells are less related to cancer itself and more to the cancer treatment. Strong chemotherapy drugs can make your urine have a strong or unpleasant odor. It can be even worse if you are dehydrated. Foul-smelling and dark-colored urine could be a sign of a urinary tract infection (UTI).

Another side effect of chemotherapy is dry mouth. Strong chemotherapy drugs can cause changes in the cells of the gums, tongue, and the inside of the cheeks. This can lead to mouth sores, bleeding gums, and tongue irritation. All of these can result in bad breath. You may also experience bad breath due to nausea and vomiting associated with chemotherapy.

3.2 How to manage odors from cancer treatment

If you think your cancer treatment is causing an unpleasant odor, you can try the following:

•    Eat fruits and vegetables to help detoxify your body. Fiber will also help you have regular bowel movements.
•    Drink plenty of water to keep your urine light in color. Staying hydrated reduces strong odors when you urinate, supports digestion, and replenishes fluids after sweating.
•    If you have a urinary tract infection, your doctor will likely prescribe antibiotics. Be sure to take them as directed.
•    Exercise based on the level your doctor recommends. Sweating is a good way to release toxins from the body.
•    Take a bath. It can help your body get rid of sweat and medication odors while making you feel fresh and clean.
•    Change your bed sheets and blankets frequently. They can start to smell from sweat, lotion, and medications.
•    Be more diligent with oral hygiene during chemotherapy to help prevent bad breath. It’s important to brush and floss regularly, but feel free to floss even if your gums are bleeding.
•    Let your doctor know if you experience frequent vomiting. Prescription anti-nausea medications can reduce or eliminate vomiting, which is a cause of bad breath.

Chemotherapy drugs have a smell. Some of them are stronger-smelling than others. The scent seems to follow you around because your sense of smell is more sensitive than usual. Others may not notice the smell.
Some chemotherapy drugs can alter your sense of smell. Some fragrances you used to enjoy, such as your favorite foods, may now be quite unpleasant. This can affect your appetite and lead to weight loss. Your sense of smell will return to normal within one or two months after your final chemotherapy session. Don’t hesitate to talk to your oncology team about your concerns. They may recommend medications or lifestyle changes to help you feel more comfortable and alleviate any discomfort.
Any smells caused by chemotherapy typically start to fade after your final round of treatment.

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References:
•    Mortimer J, et al. (2014). Does chemo make patients smell bad? bottomlineinc.com/does-chemo-make-patients-smell-bad/
•    Side effects of cancer treatment: Urinary and bladder problems. (2018). cancer.gov/about-cancer/treatment/side-effects/urination-changes
•    Sonoda H, et al. (2011). Colorectal cancer screening with odour material by canine scent detection. gut.bmj.com/content/60/6/814.full
•    What does cancer smell like? (2016). uef.fi/en/web/uef-bulletin/cancer