The Scent of the Body: Secrets and Little Secrets

A bit about each.

Our genetics are involved in this question, and there is evidence that twins, who do not even live together, have a similar smell. It has long been known that that the attractiveness or unattractiveness of our odor to the opposite sex is partly related to the degree of genetic relatedness in the MHC (major histocompatibility complex genes determine the functioning of the immune system — this is about recognizing self vs. non-self: combating pathogens, cancer cells, acceptance or rejection of transplants and embryos). In other words, we tend to prefer scents of members of the opposite sex who are less genetically related to us. This is a kind of signal indicating a higher chance of healthier and stronger offspring.

Genetics can sometimes be quite cruel: there is even a disease called trimethylaminuria. It is a mutation in the gene of the enzyme that actually converts trimethylamine. It accumulates in tissues and in all its fluids gives the body an unpleasant sharp smell of rotten fish. Nobody wishes that on anyone...

As for other factors that are a bit easier to control – diet. Depending on how much and what metabolic traits we have, foods rich in sulfur, including onions, garlic, kohlrabi or even broccoli, can cause our body to emit an unpleasant odor [to a body]. Also in one study it was shown that the odor of sweat of men who did not consume red meat was rated by female subjects as more pleasant, more attractive, and less intense. Men who consumed more fruits and vegetables also smelled more pleasant to women. In the same study, higher carbohydrate intake was associated with more intense and unpleasant sweat odor (and if your hearts, like ours, melt at the sight of pastries, now you can find an argument for self-motivation). Alcohol also negatively affects body odor [link].

Hormonal status, as expected, also defines body odor: the sweat odor of women during the [ovulatory] phase was rated as more attractive by men. Interestingly, the use of hormonal contraceptives reduced the magnitude of this difference.

Depending on our emotional state, we can also truly smell happiness or fear, as shown by some studies.

And, of course, the smell of our sweat is influenced by bacteria living on the surface and in the upper layers of our skin. But more on that a little below.

Where does the smell come from?

The smell of our body is defined by the odor of our skin secretions. We have three main groups of glands — eccrine sweat glands, apocrine sweat glands, and sebaceous glands. Eccrine sweat glands are the most numerous and open their ducts directly onto the surface of the skin. These glands especially actively work when we are hot and during physical exertion.

Unlike eccrine glands, apocrine glands begin their activity during puberty and are located quite locally — in the armpits, the groin area, and around the nipples. Apocrine sweat glands open their ducts into the hair follicle, and from there along the hair shaft their contents reach the surface of our skin. Their secretion consists of a large amount of many organic components, the variety of which depends on all the factors described above. An important fact — bacteria live not only on the surface of our skin, but also inside these glands themselves. There are many and various microorganisms there. Their diversity is greatly influenced by our hygiene habits and the use of cosmetic products.

Most of the organic compounds released by apocrine sweat glands themselves do not have a smell. And it is the bacterial enzymes that cut those large molecules into their small parts, and it is they that become volatile and do not always have a pleasant aroma.

Studies show that the most common residents of our armpits are Staphylococcus and Corynebacteria. Under the influence of cosmetic products, the biodiversity of our skin diminishes and the selection of microbial groups that can endure such daily stress is reduced. Some researchers note that the cause of unpleasant odor and increased sweating is a disbalance of the microbial balance toward an increase in Corynebacterium. And if it helps someone, here are the names of our stinkiest neighbors: Staphylococcus hominis, Corynebacterium tuberculostearicum, and Anaerococcus spp.

It is specifically the apocrine glands that are engaged when we sweat due to stress. The evolutionary purpose of this kind of “facial” trait is to quickly moisten the hairy covering to escape from a predator. At the same time it is important to deter it with some kind of unpleasant odor, so as to seem less tasty as prey. Therefore sweat from stress is indeed a nuisance! At an important meeting we are unlikely to be eaten, but we have not yet evolved to release soothing lavender scents.

“Please Santa, Antiperspirants”

The past century taught us to shave armpits and use products that suppress sweating and odor formation. The most popular of these are antiperspirants and deodorants.

The active substance in most antiperspirants is aluminum salts. When they contact the electrolytes of our sweat, they acquire a gel-like consistency and seal the sweat glands. Consequently, sweat secretion is reduced. But… if eccrine glands can be blocked relatively easily in this way, eccrine glands that open into the hair follicle are harder to neutralize. Because hair, though very slowly, grows. Therefore, sadly, antiperspirants do not always save us from “emotional” sweat excerpts.

Deodorants contain various antimicrobial substances that inhibit the growth of bacteria. They do not prevent sweating, but can be somewhat more effective in combating a particularly unpleasant smell.

And both types of products significantly affect the microbiome of our skin. Paradoxically, some studies show that using deodorants and antiperspirants may actually contribute to an excessive growth of actinobacteria and worsen the odor situation!

The most effective way to overcome these conditions might be the development of probiotic cosmetic products based on strains of microorganisms that do not tend to cause unpleasant odor.

Are antiperspirants safe?

Aluminum salts are indeed toxic and can trigger the development of some types of tumors and brain disorders — IF they penetrate into the blood. Studies show that aluminum from antiperspirants does enter the blood, BUT, ATTENTION, in extremely small amounts, which is about 2-3% of all the aluminum that enters our blood from the intestine via the food we typically eat under normal conditions and in the same time frame. There is currently no confirmed link between the development of breast cancer and Alzheimer's disease and the use of antiperspirants and deodorants. But there are data about a significant association between ovarian cancer and the use of talc in the groin area. And one must be careful with aerosols, as they can seriously poison you and even kill you, which happens occasionally.

So — practical conclusions:

If the odor from your underarms does not bother you or others, you do not complain of excessive sweating — we can congratulate you and invite you to leave your contact if we indeed undertake the development of probiotic skin products and invite you to be a donor of the microbiome! (but also remind you that there are situations when a person simply loses their sense of smell — due to head injuries or, for example, tobacco use and just cannot notice their own unpleasant odor. We have written about this here.

If the topic of underarm odor is indeed relevant to you, we can suggest the following:

• Diet: if you consume an excessive amount of products that can contribute to unpleasant body odor, it makes sense to limit them (alcohol, carbohydrates, garlic, onions, kohlrabi, red meat);
• Exercise: working out makes all sweat glands function well and somewhat “wash them out,” accordingly — fewer microorganisms, fewer of their metabolic products, less odor; Also always wear clean clothing for workouts;
• If "emotional" sweat is your nightmare, consider removing hair in these areas. But it should be removed with the roots (for example, laser hair removal) — fewer hair follicles and fewer apocrine glands and less odor. Shaving, unfortunately, almost never solves it.
• When using deodorants and antiperspirants, carefully READ and FOLLOW the instructions, do not apply products to damaged skin; As mentioned — try to avoid aerosol products — for your own safety and others. When choosing a deodorant, pay attention to the antimicrobial active ingredient, better if it is alcohol. Do not use talc in the groin area;
• Prefer cotton clothing with ventilation holes. As an option — try using special underarm shields to protect clothing from sweat. Persistent stains on clothing are formed by cosmetic products, not sweat, so if you are dealing with such a problem, try another deodorant or antiperspirant.

And finally — don’t worry, smile, and remember that sweating is a natural process. If it reassures you :)*