Body odor (or B.O., bromhidrosis, osmidrosis or ozochrotia) is a perceived unpleasant smell our bodies can give off when bacteria that live on the skin break down sweat into acids - some say it is the smell of bacteria growing on the body, but it really is the result of bacteria breaking down protein into certain acids.
Body odor usually becomes evident if measures are not taken when a human reaches puberty - 14-16 years of age in females and 15-17 years of age in males. People who are obese, those who regularly eat spicy foods, as well as individuals with certain medical conditions, such as diabetes, are more susceptible to having body odor.
People who sweat too much - those with hyperhidrosis - may also be susceptible to body odor, however, often the salt level of their sweat is too high for the bacteria to break down - it depends where the excess sweating is occurring and which type of sweat glands are involved.
Sweat itself is virtually odorless to humans; it is the rapid multiplication of bacteria in the presence of sweat and what they do (break sweat down into acids) that eventually causes the unpleasant smell. The smell is perceived as unpleasant, many believe, because most of us have been brought up to dislike it. Body odor is most likely to occur in our feet, groin, armpits, genitals, pubic hair and other hair, belly button, anus, behind the ears, and to some (lesser) extent on the rest of our skin.
Body odor can have a nice and specific smell to the individual, and can be used - especially by dogs and other animals - to identify people. Each person's unique body odor can be influenced by diet, gender, health, and medication.
Two types of acid are commonly present when there is body odor:
- Propionic acid (propanoic acid) is commonly found in sweat - propionibacteria break amino acids down into propionic acid. Propionibacteria live in the ducts of the sebaceous glands of adult and adolescent humans. Some people may identify a vinegar-like smell with propionic acid, because it is similar to acetic acid, which gives vinegar its sour taste and pungent smell.
- Isovaleric acid (3-methyl butanoic acid) is another source of body odor as a result of actions of the bacteria Staphylococcus epidermidis, which are also present in several strong cheese types.
Sweating and our sweat glands
The average human body has three to four million sweat glands, of which there are two types:
A type of simple sweat gland that is located in almost all areas where there is skin. They produce sweat that reaches the skin's surface via coiled ducts (tubes). When sweat evaporates from the skin the body is cooled. Eccrine glands are responsible for regulating our body's temperature.
Apocrine glands are located in several areas, including the armpits.
These glands are found in the breasts, genital area, eyelids, armpits and ear. In the breasts they secrete fat droplets into breast milk. In the ear they help form earwax. Apocrine glands in skin and the eyelids are sweat glands.Most of the apocrine glands in the skin are located in the groin, armpits and around the nipples of the breast. Apocrine glands in the skin usually have an odor; they are scent glands.
Experts say that pheromones subconsciously influence how we react to each other; one human may find another sexually attractive because the smell of their pheromones is attractive to him/her. The apocrine glands are mainly responsible for body odor because the sweat they produce is high in protein which bacteria can break down easily. The eccrine glands produce sweat which is high in salt, making it harder for bacteria to break down the protein. In other words, a lot of our B.O. (body odor) comes from the sweat produced by our apocrine glands.
What causes foot odor?
Most of us wear shoes and socks, making it much more difficult for the sweat to evaporate, giving the bacteria more sweat to break down into smelly substances. Moist feet also raise the risk of fungi developing, which can also give off unpleasant smells.
Diagnosing body odor
In the vast majority of cases of body odor it is not necessary to see your doctor. The individual himself/herself may be aware of it, or a good friend or a member of the household may tell them about their body odor. There are some self-care techniques that will usually successfully treat the problem.
When to see your doctor about body odor
Some medical conditions may change how much a person sweats, while others can alter how we sweat, subsequently changing the way we smell. For example, hyperthyroidism (an over-active thyroid gland) or the menopause can make people sweat much more, while liver disease, kidney disease, or diabetes can change the consistency of sweat so that the person smells differently. You should see your doctor if:
- You start sweating at night
- You start sweating much more than you normally do, without any logical reason
- You have cold sweats
- Sweating disrupts your daily routine.
You should also see your doctor if your body smells differently. A fruity smell could indicate diabetes due to high levels of ketones in the bloodstream. Liver or kidney disease can often make the individual have a bleach-like smell due to a build-up of toxins in the body.1-3
On the next page, we look at the treatments for body odor and the ways in which it can be prevented.