10 Sources of Body Odor That Aren't Just Sweat

Trimethylaminuria is a rare genetic disorder in which the body is unable to break down the chemical compound trimethylamine. The latteris produced by bacteria in the intestines during the digestion of proteins from eggs, liver, legumes such as soybeans and peas, some varieties of fish, and other foods. Normally, an enzyme breaks down trimethylamine, which has an odor that's been likened to rotting fish or eggs, garbage, or urine [source National Library of Medicine].

But people with trimethylaminuria, because of a mutation in the FM03 gene, either lack the ability to produce the enzyme or make too little of it. In a few cases, even people with the normal gene can develop a similar odor, because of an excess of dietary protein or liver or kidney disease [source: National Library of Medicine]. The result is that patients give off a very strong fish-like smell. There's no cure for trimethylaminuria, but people may be able to curb the odor by avoiding the products listed earlier and taking certain supplements and antibiotics [source: NIH].

That odd aroma that you notice when you're visiting your great aunt isn't just from mothballs or musty, old books. Researchers at the Monell Chemical Senses Center in 2012 found that elderly people actually have a distinctive scent, which they believe is caused by changes in skin glands and their secretions as we grow older.

Old-person smell may be a sort of chemical signal developed during human evolution, which enables us to differentiate between younger, stronger individuals of breeding age and older, less healthy ones who may be less desirable partners.

On the plus side, the volunteer smell-testers rated the odor of old men as less pungent and unpleasant than the body odor of middle-aged men [source: Sifferlin].

Strangely, oral contraceptives may alter the aroma of females who take them. That's according to an animal study published in 2010 in the scientific journal, Proceedings of the Royal Society B. Researchers at Duke Lemur Center studied the effect of medroxyprogesterone acetate, usually known by its brand name of Depo-Provera, on 12 adult female ring-tailed lemurs, and found that that the contraceptive altered the chemical composition of secretions from the lemurs' genital areas, making their scent less attractive to male lemurs [source: Bates].

Does the same hold true for humans? People are known to send and receive olfactory cues about hormonal status, and the Duke researchers said more study would need to be done to see whether humans can detect whether someone is on birth control through scent.

Meanwhile a 2008 study showed that being on birth control pills can affect a woman's taste in men. Women were asked to smell T-shirts worn by men and pick the ones they were most attracted to. They overwhelmingly picked ones for men whose immune systems were different from theirs. From an evolutionary point of view, this is a good thing as it ensures a more diverse gene pool. However, when the women were on the birth control pill, they tended to pick men with similar immune systems. Could that mean that they might end up with the wrong man? [source: Nalls]

If you've ever eaten a spicy meal and then gone to the gym later in the day for a hard, sweaty workout, you may have noticed that other exercisers gave you a wide berth. It's not just because of your breath. Foods containing curry, garlic and various other spices are metabolized by your body to produce stinky chemicals such as sulfur, which ooze out of your pores to create a pungent body odor.

Some food ingredients such as capsaicin, the hot pepper used in Buffalo-style chicken wings, make matters worse by stimulating the nerve receptors in your mouth and tricking your nervous system into thinking that your body is outside in 90 degree F (32 degree C) heat, so that you start sweating more than usual [sources: Watson, Kosecki and Gelman]. So if you're going to indulge in a peppery, curry dish, you might want to go for a walk in the woods by yourself rather than hit the gym.

If untreated, various types of cancer can cause the development of necrotic lesions — that is, dead, rotting tissue — that give off a powerful odor. For instance, a man who suffered from an undiagnosed cancer in his penis developed such a powerful stink that his office colleagues refused to work with him – which was the only reason he sought medical help. His doctor hypothesized that some substance was being drawn from the necrotic lesion and released through the sweat glands [source: Liddell].

Another patient with psychosis had such a bad body odor that her psychiatrist could smell her even before she got to his office. "It turned out that this poor lady had advanced breast cancer, with a lesion that was eating through the breast and oozing foul-smelling necrotic gunk," the doctor wrote. "She was too psychotic to know what was happening." But after the psychiatrist got her to have cancer surgery and put her on antipsychotic medication, both the odor and her mental confusion subsided [source: Cohen].

Sometimes, diabetes can be a cause of body odor. When untreated, this disease can cause a condition called diabetic ketoacidosis. Without enough insulin to regulate the metabolism, the body starts to break down fat for fuel. This causes a sickeningly sweet aroma comparable to decomposing apples. It's most obvious on a person's breath, but it's also given off by the body as well [source: Liddell].

That's why when a patient seeks treatment for body odor, physicians may order blood or urine tests to determine if there is an underlying medical condition such as diabetes [source: Mayo Clinic].

Do you smell baking? According to a 1976 medical journal article, patients afflicted with typhoid fever "emit a smell comparable to freshly baked brown bread" [source: Liddell]. That may actually sound kind of pleasant, but rest assured that typhoid fever is anything but.

Patients with this disease usually develop a sustained fever as high as 103 to 104 degrees F (39 to 40 degrees C), and suffer stomach pains and headaches, as well as weakness. In some cases, they also experience a rash of flat, rose-colored spots. About 21.5 million people die from typhoid fever each year, mostly in developing countries. It's spread by eating food or drinking water handled by someone who already has the disease and is shedding the Salmonella Typhi bacteria [source: CDC].

As we've mentioned before, infectious diseases often cause changes in body odor. But immunizations, interestingly, can have similar effects. In an animal study published in 2014 in the journal Physiology and Behavior, researchers from the Monell Chemical Senses Center and the U.S. Department of Agriculture demonstrated that immunization can trigger a distinct change in scent. Scientists believe that humans and other animals may give off "immune-activated odors" as a way of signaling to other members of their species that they have become infected with diseases. (This could also explain why certain diseases have specific odors).

Researchers found a pathway between immune activation and changes in body odor compounds, and believe that eventually, it may be possible for doctors to use odor to "eavesdrop" upon the immune system and make noninvasive diagnoses [source: ScienceDaily].

If you're thinking about trying a caveman-style "paleo" diet, in which you would eat a whole lot of meat and sharply cut your carbohydrates, you may want to consider the effect on your aroma. In a study published in the journal Chemical Senses in 2006, 17 male subjects ate a diet containing red meat for two weeks and sweated into pads, which a panel of women volunteers then sniffed to evaluate the aroma. The subjects then switched to a diet without red meat for a similar period, and were subjected to a second smell test for comparison.

The researchers reported that "the odor of donors when on the non-meat diet was judged as significantly more attractive, more pleasant, and less intense." Which implies that red meat consumption has an adverse impact upon one's scent [source: Havlicek and Lenochova].

While your nose picks up the chemicals that create aromas, it's your brain that actually tells you what you smell. That's one reason that patients who suffer from Alzheimer's disease and other neurological disorders sometimes experience a loss of their olfactory abilities [source: Doty].

What's even more surprising, though, is that mental illness can make you believe that you smell terrible, even if you don't. Olfactory Reference Syndrome is a psychiatric disorder characterized by a false belief that you have a bad body odor. Eighty-five percent of people with the disease report that they actually can smell their own imaginary stink [source: Phillips and Menard].