Body odor from a scientific perspective

Most of us are very sensitive to body odor, just a light inhalation can detect that unpleasant odor. Inside that smell is a very complex mechanism influenced by genes, age, diet and personal hygiene. So what exactly is body odor? Where does it come from? And what can we do with it?

To get started, you only need two things to create that familiar scent: the sweat secreted under your armpits and the bacteria that live on it. Most people release body odor through sweat and that’s the crux of the matter. Your body has millions of sweat glands, divided into two main types:

Body odor from a scientific perspective
We are all very sensitive to body odor.

The sweat that the Apocrine glands secrete is mainly protein and fat. This type of sweat is usually odorless if no bacteria are present. Every square centimeter of our body is covered with thousands of bacteria. Many microorganisms thrive in moist environments, like the underarms. Bacteria here can number in the millions per square centimeter, one of the most densely populated areas on the entire skin.

​Hidden among these microorganisms are Corynebacteria, Staphylococci, and Micrococci. These bacteria live off the protein and fat in sweat. They turn odorless compounds into new compounds with very unpleasant odors. One of the biggest contributors is probably the sulfur compounds that give body odor the smell of onions, and the carboxylic acids that give the cheese the smell.

These molecules radiate from under the armpits and can get right into the nose, where they get trapped and are immediately detected by special receptors. We can detect odor-causing molecules at concentrations < 1/1,000,000.

Body odor from a scientific perspective
Most people release body odor through sweat.

Body odor varies from person to person, depending on how many microorganisms live under the armpits and what nutrients the sweat glands provide them. Genomics also helps determine which compounds you secrete, and in what amounts, adrenaline increases the rate of sweat, so body odor can become stronger when you’re nervous. The structure and density of bacteria also varies from person to person and plays an important role. Even the food you eat has a small effect.

Cleaning the underarm area with soap and water improves but does not remove bacteria because there is still a lot hidden under the deeper skin layers. Deodorant restricts bacteria from working at the same time, creating a deodorizing layer. Antiperspirants create sweat glands that clog the sweat glands, drying out the underarms.

While we continue the war, scientists are still trying to understand it. We don’t know why the brain is so often bothered by these particular smells. But many theories suggest that the smell of sweat from the underarm area may have positive functions such as strengthening social ties and providing a special communication tool.