Sweat is actually nearly odorless. The body smell or body odor is actually caused by the bacteria feeding on the salts in the sweat, which leads to the creation of foul smelling acids.
Most people blame body smell or body odor on sweat. However, what most people don’t realize is that sweat is nearly odorless. So what causes body odor? Believe it or not, it is actually the bacteria that are blame for the stinky smell. Bacteria love to feed on the proteins and other nutrients that are dissolved in sweat. Sweat is mainly a solution of water and salts, and the bacteria break down the salts and nutrients into acids, which is a byproduct of their digestive system. These acids are actually what give the stinky odor to the sweat.
Most people blame body odor on bad personal hygiene practices, such as not taking enough showers or not washing their clothes regularly. However, the worst culprit for causing body odor and the most common is actually stress.
The body actually has two different types of sweat glands: eccrine glands and apocrine glands. Together they amount for the 3 to 4 million sweat glands on the body. The eccrine glands are glands that are spread out all over the body. These glands are responsible for cooling the body. How they work is when the body temperature rises, these glands release the nearly odorless sweat onto the surface of the body. When the sweat evaporates, the process of evaporation cools the body down
Now, the apocrine glands are glands that are located in the hairy parts of the body, such as the armpits and genital area. In fact, the springy hairs found in this area actually help to diffuse the body odor. When we are stressed, these apocrine glands release sweat. As these areas are hubs for bacterial growth, they feed off of the sweat creating body odor. The bacteria in fact love this type of sweat because it has less water content and more salt content, hence more delicious and nutritious for the bacteria.
Body odor actually would have developed as an important survival function in our ancestors, as a strong body odor can be a warning signal for predators to stay away, or it can be also a signal that the prey animal, i.e. us is unpalatable, so that the predator is better off hunting for something else.
Body odor can also actually serve as an important indicator of overall health and dietary habits. A diet rich in milk, cheese, meat, animal fats and refined carbohydrate products like white flour can result in a specific type of body odor. Additionally, many other surprising factors can also account for body odor. These include not toweling off or drying off properly which leads to moisture getting trapped in the folds of the skin, which in turn leads to increased bacterial growth. Food particulates also get trapped in the thousands of small hairlike projections called papillae that are present on the tongue. These food particulates can aid bacteria growth hence leading to emission of hydrogen sulfide vapors which cause bad breath.
Genetic disorders such as trimethylaminuria, in which the body is unable to break down a chemical compound called trimethylamine, or ultra-moist feet, which attract a specific bacteria that releases sulfur-smelling compounds, can also result is a specific type of body odor. Also, certain diseases or medical conditions may cause the body to release certain specific compounds, these conditions include diabetes, cancer, high or low blood sugar, certain vitamin and mineral deficiencies, constipation, infections, and/or taking birth control pills.
Also believe it or not using antiperspirants, deodorants, body washes, body sprays, and lotions can actually cause increased and/or worse body odor. This is due to some of the ingredients that are used in these products that end up covering the body smell but may actually encourage bacterial growth, hence working counter intuitive.