Ever caught a whiff of someone and thought, “What on Earth is that?” Or worse, wondered if it’s you? Don’t worry, we’ve all been there. Body odour is a universal phenomenon, but why do some people seem to carry around their own… distinct aroma? Is it their diet? Their genes? Or maybe their shower habits (or lack thereof)? The truth is, sweat itself doesn’t stink—it’s what happens when your skin, bacteria, and a dash of chemistry get together for a party. Let’s dive into the amusing, slightly stinky world of body odour, uncovering why some of us smell like roses while others are, well, a bit more ripe.
It’s in your genes
We all have the ABCC11 gene, which helps transport molecules in and out of cells, including those in sweat and earwax. When the gene is active, it helps sweat molecules reach the skin’s surface, where bacteria can break them down, leading to body odour. When this gene doesn’t work properly, sweat molecules can’t reach the armpit, and body odour doesn’t form.
The ABCC11 gene also affects earwax production: those with the defect (or A allele) have dryer earwax while those with the functioning gene (or G allele) have wet, yellowish-brown earwax.
Variations in the ABCC11 gene can affect how much sweat is produced and the types of compounds in it, which in turn influences how much odour is produced. For example, the “wet earwax” variant, which is common in people of African and Caucasian descent, is linked to stronger body odour, while the “dry earwax” variant, found more often in East Asians, tends to result in less body odour.
In Japan, wet earwax has traditionally been linked to stronger body odour. A study by Yoo et al. (2006) found that 860 out of 896 people who saw a doctor for stinky armpits had wet earwax, even though wet earwax is rare in that population.
Turns out that 80–95% of East Asians have the non-functional A allele ABCC11 gene, while very few Caucasians and Africans (about 2-3%) have this genotype. The landscape is more complex when looking at people from the Pacific Islands, South and Central Asia, where 30-50% have dry earwax types.
This mutation in the ABCC11 gene originated when humans migrated out of Africa 70,000-100,000 years ago. Researchers suggest that East Asian ancestors likely lived in colder environments than Africans, and individuals with the A allele may have had an advantage by sweating less to help them adapt to the cold climate. This allele has been passed down through generations of East Asians, including Koreans, Han Chinese, Mongolians, and Yamato Japanese. However, the dry earwax trait can only be inherited if both parents carry the same gene.
What does ethnicity have to do with it?
A person’s body odour can also be partly influenced by their ethnicity. In fact, a 2017 study looking at three different ethnic groups (African-American, Caucasian, and East Asian) found that the main body odour smells from the armpits vary depending on a person’s ethnicity.
While the ABCC11 gene has to do with whether or not someone has a high or low level of body odour, other factors determine the specific “scent” of the odour. The scent is determined by the volatile organic compounds (VOCs) – the stinky airborne chemicals detectable by our noses. VOCs are produced when sweat is broken down by the bacteria on our skin. The specific VOCs released determine the type of odour we perceive—whether it’s sour, musky, or even cheese-like. For example, VOCs like isovaleric acid give off a sweaty or cheesy smell, while others, like thiols, can produce a sulfur-like odour.
The type of body odour can be influenced by microbiota—microorganisms like bacteria, fungi, and viruses that live on and inside our bodies—through variations in microbial composition, sweat composition, and genetic factors that affect how microbes metabolise sweat and skin secretions.
A 2018 study by Vanderbilt University found that the most significant predictor of gut microbiota composition is ethnicity, which encompasses both genetic inheritance and cultural influences, such as diet (like food they’ve eaten since childhood). Numerous studies have also shown that the skin microbiome varies significantly across different ethnicities. Differences in the skin microbiome, like fewer Staphylococcus bacteria and more Corynebacterium, have been connected to genetic differences between people from East Asia and those from Europe or Africa, especially when studying armpit bacteria.
Since sweat needs to interact with skin bacteria to be odourous, it’s no surprise that different bacterium produce different odours. Corynebacterium and Staphylococcus hominis are the main culprits behind strong armpit odours: Corynebacterium primarily contributes to sour and musky scents, while Staphylococcus hominis is responsible for sharper, onion-like smells.
Is it in the food we eat?
While there is truth to “we are what we eat,” it’s worth noting that when it comes to body odour, it may not be as simple. The reason may be either genetic or something related to their unique microbiota.
Having said that, some foods have a tendency to make us smell either better or worse. A 2006 study found that men who consumed a non-meat diet had body odour that was judged as more pleasant, more attractive, and less intense compared to when they consumed red meat. A 2016 study found that men who consumed fruits and vegetables were associated with pleasant-smelling sweat according to women, while self-reported data showed that meat, egg, and tofu intake also improved sweat smell. However, a high carbohydrate intake made sweat smell less pleasant and stronger.
Certain foods are also proven to change your body’s scent by enhancing the bacterial production of smelly metabolites. Cruciferous vegetables like broccoli, kale, and cabbage are high in fibre and also high in sulfur-containing substances that break down into hydrogen sulfide, which has a rotten egg kind of smell. When your body breaks down garlic, onions, and herbs and spices like curry and cumin, sulfur-like compounds are produced and they react with sweat on your skin to produce body odour. Even alcohol can cause body odour because our bodies metabolise alcohol into acetate, which contributes to greater body odour when it gets secreted into sweat.
The boys vs girls
If you’ve ever wondered why men tend to smell a bit stronger, it’s this: men tend to have larger sweat glands and generally produce more sweat than women. This increased sweat production creates a perfect environment for certain bacteria, particularly Corynebacterium species, to thrive. These bacteria feast on the sweat, especially the proteins and lipids it contains, and produce volatile fatty acids as byproducts. It’s these fatty acids that give off odour, which tends to be stronger in men due to their higher sweat output.
So, if you’ve ever wondered why men’s body odour can be more intense, it’s largely because of their sweat glands and the bacteria having a bit more of a feast.
Disease detection via body odour
If you have an intensely foul body odour a few hours after eating seafood, this means it’s most likely a metabolic disorder called trimethylaminuria, which affects 1 in 1 million people worldwide. This is because the body can’t break down the chemical trimethylamine that’s naturally found in seafood. Those with the disorder may also need to avoid other foods that contain precursors to trimethylamine, such as eggs, liver, legumes, and milk from grass-fed cows.
Also, since your liver is responsible for processing bacterial metabolites, converting strong-smelling substances (eg. trimethylamine) into less odorous or odour-neutral compounds (eg. trimethylamine oxide), impaired liver function can reduce this detoxification capacity. Your kidneys also excrete bacterial metabolites and their substrates from the bloodstream, so a dysfunction can lead to an accumulation of these compounds, increasing body odour.
This means that body odour can actually reveal the presence of diseases – for instance, cholera smells sweet and acute, while diabetes smells like rotten apples.
What’s the “old people smell”
“Old people smell” refers to a distinct odour often associated with aging, typically described as musty, stale, or greasy. The primary cause of this smell is a compound called 2-nonenal, which is produced when fatty acids in the skin break down. As we age, our skin produces fewer natural oils, and oxidative processes increase, leading to the accumulation of nonenal, which gives off a characteristic odour.
This smell is also influenced by changes in sweat production and hormonal shifts that occur in older adults. As sweat glands become less active and produce less sweat, the odours associated with bacteria in sweat diminish, but 2-nonenal becomes more noticeable.
Interestingly, the “old people smell” largely transcends ethnicity, as it is a natural part of the aging process that affects everyone, regardless of background. While the intensity and perception of this smell may vary slightly due to factors like diet, hygiene, or individual skin characteristics, the underlying cause—oxidative breakdown of fatty acids in the skin—remains consistent across ethnicities. Therefore, the “old people smell” is not specific to any one ethnic group but rather a biological phenomenon tied to aging.
So how do we reduce body odour?
When it comes to body odour, our ethnicity, diet, and the bacteria living in our armpits all play a role in determining whether we smell like roses or, well, something a bit more… pungent. So, it’s not just about the genes we inherit, but also the invisible microbial community we carry around with us that can give us that unique “scent” signature.
Combating body odour involves a mix of good hygiene, lifestyle changes, and sometimes specialised treatments. In addition to showering regularly and drying off properly, using products like antiperspirants (which contain aluminium salts to reduce sweat production) and deodorants (which mask odours and often contain antibacterial agents) will help. You can also use home remedies like baking soda and cornstarch – simply form a thick paste, apply this to your underarms for 5-7 minutes, and rinse it off with cold water. Baking soda neutralises odour-causing bacteria while cornstarch absorbs moisture from the skin.
