What causes body odour
Body odour. No matter what the time of the year, it just plagues some people.
When you smell somebody's B.O., it's easy to assume they have just been exercising, have poor hygiene or simply don't use deodorant.
Lots of other factors can influence the way you smell, however. Body odour, also known as bromhidrosis, osmidrosis or ozochrotia, is a smell we think of as offensive and occurs when the bacteria that lives on the skin breaks down sweat into acids.
Sweat itself is odourless; it's simply the bacteria breaking down the protein in it that causes the bad smell. Two different acids usually cause this smell: propionic acid and isovaleric acid.
Propionic acid is what breaks down from propionibacteria, which lives in the sebaceous gland ducts. It has a particularly vinegary smell. Sovaleric acid, on the other hand, results from the bacteria Staphylococcus epidermidis, and has a pungent, cheesy smell.
We humans have two types of glands, eccrine and apocrine. Eccrine glands are those responsible for regulating our body temperatures; they're all over your skin. The sweat produced from these glands is salty and harder for bacteria to break down the protein in them.
Apocrine glands around found in your armpits, genitals, breasts, eyelids, and ears. The sweat from these glands is much more easily broken down into protein by bacteria, which quickly multiplies and causes the majority of body odour.
There are several factors that can influence how much you smell (and how offensive that smell is) when those apocrine glands are working their way into bacterial overload.
Genetics, like with many bodily functions, are a core influencer of one's B.O. The gene ABCC11 is responsible for axillary body odour and the more functional this gene is, the more encouraging it will be for bacterial growth from your apocrine glands.
This is also determined by your heritage: around 80-95 per cent of people with East Asian backgrounds (Chinese, Japanese, Korean) have a non-functioning ABCC11 allele, meaning lower likelihood of producing body odour. Most other ethnic groups only have 0-3 per cent have this non-functioning allele, so the large majority of those groups are prone to axillary odour.
A genetic condition called trimethylaminuria, which is colloquially known as "fish odour syndrome", may also be the culprit. Although rare, this metabolic disorder hinders your body's ability to break down trimethtylamine (found in choline-rich foods like eggs, certain fish, and some legumes). When trimethtylamine builds up in the body, it creates a fishy stink.
A dietary imbalance of magnesium or zinc can contribute to offensive body odour as well. One of the main things zinc does is processes carbohydrates into waste, but if you don't have enough of it, this clearing process is hindered and odours can ensue. Low magnesium, additionally, causes slower emptying of the bowel and this can also have an effect on your body odour.
Then there's certain foods that can contribute to negative odour. Red meat, garlic, onions, broccoli, Brussels sprouts, and strong spices such as curry powder can also encourage negative odours, as can alcohol, tobacco, and caffeine.
What can you do about offensive body odour?
Frequent showering is the obvious one, but for those that struggle this simply isn't enough. One solution can be to reapply deodorant multiple times a day. Clinical strength antiperspirant deodorants may prove helpful but prescription versions from a GP may also be more helpful than over-the-counter products.
Body odour also clings to material, so fresh clothing and natural fabrics that breathe (e.g. cotton rather than synthetic blends) can mitigate odours and give them less time to permeate. Sweat will also evaporate quicker through natural fabrics. Shaving your armpits, too, gives the odour less to stick to, and don't rule out a midday change to a fresh shirt.
There's nothing you can do about your genes, but you can reduce or cut out the aforementioned foods and gauge the change in the way you smell. You may find one of them, all of them, or a combination affect you.
Written by Lee Suckling. First appeared on Stuff.co.nz.