Everything has a characteristic smell – food or otherwise. Our highly functional noses are excellent at their jobs of detecting smells and transmitting the signal to our brains. This function was extremely crucial for ancient humans to hunt for food that would not be poisonous and detrimental to health. However, smells even aided in social bonding – particularly, the smell of our bodies.
Circling back to the first sentence, everything and everyone has a smell. The human body is not unique to produce a smell – animals, birds, and nearly all organisms have a smell attributed to them. For simple organisms such as unicellular microorganisms, the smell is a characteristic of their cellular products. As for higher organisms such as animals, their smell is a result of their diet and hygiene. Since humans are social animals, but a bit more advanced than other animals, several factors play a role in determining the smell of our bodies. These factors are GENETICS, age, hygiene, and diet.
The odor being referred to here is the natural smell of our body, without the application of soap or deodorant. Often, body odor is associated with SWEAT. It is common knowledge that sweating natural process to avoid overheating the body in hot climates. Our SWEAT GLANDS, which line each part of our EPITHELIUM (skin), release chemicals which we are collectively known as sweat to cool the body.
Does sweating cause body odor?
The common misconception about sweating is that it causes body odor. Sweating does not cause body odor but may contribute to it. Sweat glands are of two types – ECCRINE and APOCRINE. The eccrine glands line each part of our skin – nearly two sq. meters – and is the primary gland to avoid overheating. The sweat it produces is in the form of water and salts, which evaporate, leaving the skin cool.
Since water and salt (even in day-to-day life) have no odor, the sweat produced by the eccrine gland does not cause body odor. On the other hand, the apocrine gland is particularly found in the armpits and groin. The apocrine gland has no reservation to cool the body off – it actively produces sweat under emotional stress. This is why people start to sweat when nervous.
Apocrine glands produce sweat which is rich in proteins and fats. Proteins and fats, in general, do not have a strong smell. Thus, the sweat produced by the apocrine gland does not correspond to body odor. However, it does contribute to the smelling of our bodies.
Why do we have a body odor?
As we know, proteins and fats are rich sources of nutrition. Since the apocrine glands are present in the armpit and the groin – which are known to contain hair follicles – the sweat-containing proteins and fats enter the hair follicles. The sweat encounters thousands of microbes in the hair follicles. These microbes are known as the MICROBIOTA of the body and line each part of our body.
The normal microbiota lives in a SYMBIOTIC relationship with the body – the association benefits both the body and the microorganisms. The microbes feed on the substances on and in the body and proliferate. They are also secure from invasion by other microbes due to the shelter of our bodies. In return, these microbes help in the immunity and other cellular processes of the body. However, in the case of body odor, these microbes essentially cause it.
It has been established that sweat has no odor. The chemicals found in sweat – water, salt, proteins, and fats – themselves do not have a smell. But when the sweat secreted by the apocrine gland enters the hair follicles, the microbiota feeds on the sweat and breaks down the proteins and fats. The resultant products formed as a result of microbial consumption are the ones that impart an odor.
The microbes thrive in the moist environments of the armpit and the groin and actively feed on the sweat, accelerating the rate at which the odorous compounds are generated. Proteins and fats are generally converted to acids, which are known to have a characteristic smell. If the proteins are high in the concentration of SULPHUR, the smell becomes stronger and more repelling. The apocrine glands are no active until PUBERTY, hence children are not susceptible to body odor.
Which other factors contribute to body odor?
As mentioned before, the factors which determine body odor are genetics, diet, hygiene, and age.
The genes received from the parents contain the code for the spread of the sweat glands. Since every chemical reaction is dependent on enzymes, the genetic code plays a significant role in determining the quantity and characteristics of the sweat being secreted. Hence, the sweat – and the resultant odor – of each person is unique. It is a popular notion that people originating from East Asia are less susceptible to body odor.
We obtain most of the compounds in our bodies from our diet. A major chunk of proteins – called ESSENTIAL proteins – are obtained from the diet and cannot be synthesized in the body. Hence, the protein content in our body (and in the sweat secreted by the apocrine glands) relies on the diet we consume. The significance of sulfur in the sweat was also mentioned. Consumption of foods rich in sulfur, such as cauliflower and broccoli, can worsen the body odor by increasing the concentration of sulfur.
Meat eaters also tend to have a worse body odor than vegetarians or vegans. Since meat contains a large number of proteins and fats, it contributes heavily to the sweat and thereby, causes the bacteria to produce a distinct odor.
Social convention dictates us to bathe daily and use deodorant. While soap and water can only clean the sweat produced, it does not stop the process of sweating. Deodorants and antiperspirants mask the body odor as well as keep the sweating in check. Antiperspirants contain compounds that can clog the sweat glands and stop the secretion of sweat. Hence, a person who uses deodorant or antiperspirants regularly would have a lesser body odor than someone who does not.
Since the apocrine glands are inactive till puberty, children do not have a body odor. Through the years of puberty and beyond, since there are several changes in the body, the composition of swear varies and thus, body odor varies. Old people tend to have a unique body odor.
Yet, ancient humans lived with their body odor, making scientists think it may have an advantage that we may not have uncovered yet. Some hypotheses suggest that the sweat produced by the apocrine gland may contain PHERMONES, which are essential for social bonding. The body is a well-oiled machine and is capable of maintaining its hygiene and its microbiota. Thus, although theoretically, body odor should not repel us, social norms dictate so.