Causes and symptoms of body odor

The mechanism by which body odor is produced by sweat secreted from eccrine sweat glands

Eccrine sweat glands are located on the surface of the skin all over the body and regulate body temperature and moisture by secreting sweat. When body temperature rises, they actively produce sweat, and even when it's not, they produce small amounts of sweat to prevent the skin from drying out. The sweat secreted from these eccrine sweat glands is almost odorless. This is because this sweat is composed of water, salt, and minerals, and contains almost no odor-causing components. In other words, sweat itself is not the cause of body odor.
However, if this sweat is left untreated, it will mix with fatty acids, dead skin cells, and resident skin bacteria, eventually leading to bacterial growth and the emission of unpleasant odors. The cause is not the sweat itself, but the lack of proper care.

Body odor is produced by sweat from the apocrine sweat glands.

Apocrine sweat glands are found only in hair follicles in specific areas such as the armpits, nipples, and genitals. Unlike eccrine sweat, apocrine sweat contains various components such as proteins, sugars, iron, ammonia, and lipids, and when mixed with fatty acids or broken down by bacteria, it emits a stronger odor than eccrine sweat. Strong body odor, often associated with underarm odor, is caused by a large number of these apocrine sweat glands. In this case, sweat care is essential, but in some cases, more drastic measures, such as surgical intervention, may be necessary.

diabetes

hyperthyroidism

Central nervous system disorders

Parkinson's disease, hemiplegia, etc.

Fish odor syndrome (metabolic disorder)

Oral inflammation

Periodontitis, stomatitis, gingivitis, etc.

Diseases of the nose and throat

Tonsillitis, chronic rhinitis, sinusitis, etc.

respiratory disease

Bronchitis, bronchiectasis, pulmonary tuberculosis, etc.

Gastrointestinal diseases

Gastritis, achlorhydria, gastric dilation, gastric ulcer, duodenal ulcer, stomach cancer, etc.

Decreased liver and kidney function

head

The scalp, with its well-developed sebaceous glands, is a prime location for strong body odor. When a large amount of sebum is secreted and accumulates on the scalp and hair, bacteria break it down, resulting in an unpleasant smell.
Furthermore, hair, especially damp hair, has the characteristic of easily absorbing odor molecules from the air. The head is the part of the body where both the body's own scent and the surrounding scents combine to create body odor.

armpit

As explained in "Causes of Body Odor," the armpits contain apocrine sweat glands, which produce sweat that tends to have an unpleasant odor. When this sweat causes a strong underarm odor, it is commonly known as bromhidrosis. It is characterized by a distinctive smell reminiscent of spices or sulfur. People with bromhidrosis tend to have large and numerous apocrine sweat glands, which secrete more sweat that leads to a stronger odor.
Furthermore, if you have underarm hair, bacteria can multiply more easily than if you don't, making you more prone to body odor.

feet

The soles of the feet, which have the thickest stratum corneum in the body, are prone to accumulating a large amount of dead skin cells. This is due to the shedding of dead skin cells through metabolism and friction. When lipids mix with this dead skin, a foul odor is immediately produced. Wearing shoes and socks for extended periods, or wearing poorly maintained, sweat-soaked shoes, can also cause mold and bacteria to break down sweat and sebum, resulting in a distinctive odor.

genitals

The area around the genitals, like the armpits, has apocrine sweat glands, which can produce a strong body odor.
In women, a foul odor can also be caused by vaginitis resulting from bacteria or Trichomonas.