Why does sweat smell different in certain periods of time?

Body and skin odors

An individual body odor is innate and changes continuously into old age. This affects our skin, our breath and our various glands and excretory organs. Smells reveal information about how we feel, what habits we have, what we eat and how our health is doing.
In politics one speaks of a stable odor, which one has to have in order to be successful in a party. The same selection happens every day when people meet or get to know each other. The body odor has a decisive influence on whether there are friendships or partnerships or whether the genes fit together or not.
In detail, however, body odors signal a lot more. Much of it we only perceive in other people, some we notice in our body ourselves. Nature gave us this perception ancient times, even before we could make ourselves understandable through language. It is used for information and the exchange of information. Among other things, one can "smell" diseases and the associated metabolic disorders.

Metabolism & Disease

Diabetics give off an acetone-like odor when they have too much sugar. In fact, acetone can be found in urine, bad breath and breath, and on the skin. The lack of insulin causes the body to break down more proteins and fats for energy. This creates acetoacetic acid and acetone. Acetone is formed in the same way in healthy people when they are hungry and there is no longer enough glucose available, i. H. hypoglycaemia and, in extreme cases, ketoacidosis. So you can also smell hunger.
Bad breath also changes in diseases of the internal organs such as the liver and kidneys. In renal insufficiency, the breath can smell like urine.
Urinary tract infections and incontinence are jokingly referred to as a smell of ammonia and pickles. In fact, the bacteria involved in the infection and those in the genital area split the urea in the urine into ammonia and carbonic acid. A similar odor occurs in the congenital metabolic disease trimethylaminuria (TMAU). Breath, sweat and urine all smell like trimethylamine. The odor also occurs in the urine of healthy people after consuming fish.
Likewise, diseases of the pancreas manifest themselves not only through a change in the color of the stool, but also through its smell.
Conditioned dogs can detect lung and breast cancer at a very early stage by the smell of their breath. Naturally, in the late stages of breast cancer, for example, there is a putrid aroma on the skin, which is caused by the death of cells. Similar relationships can be found in bedsores and open legs (diabetes). Diphtheria creates a sweet, putrid smell in the mouth. Further examples are:

  • Hypermethioninemia (disruption of methionine adenosyltransferase in amino acid metabolism) - rancid odor
  • Phenylketonuria (defect in phenylalanine hydroxylase in the amino acid metabolism) - smell of mouse feces
  • Isovaleric acidosis (defect in isovaleryl-CoA dehydrogenase in amino acid metabolism) - sweat-like odor
  • Maple syrup disease (several subspecies due to defects in the citric acid cycle and in the amino acid metabolism) - including a "Maggi" -like odor
  • The hypothyroidism can manifest itself as bad breath and sweat.
  • The smelly nose (ozaena) occurs when bacteria settle in the nose and destroy the nasal mucous membrane.
Hormones

Hormones program metabolism, body functions and sexuality from birth to death. You decide whether we look youthfully fresh, the face shows the first wrinkles, the skin loses its elasticity or the typical age skin comes to the fore. The amounts of hormones produced by the body and their relationships with one another change right up to old age - combined with corresponding influences on the skin. Changes in metabolism can also be seen in changes in body odor.
During puberty, the changed smell of sweat is particularly noticeable in young men, the main component of which is androstenone, a breakdown product of testosterone. The sweat grades of women and men differ not only because of their gender-specific hormone balance. Different substances are excreted, which in turn are converted by the skin flora and produce odors that are attractive or rather repulsive - including isovaleric acid and branched, partially unsaturated C6-C11 acids. In the case of constantly high perspiration (hyperhidrosis), bromhidrosis can develop, in which the appropriately adapted skin flora breaks down parts of the horny layer and produces particularly unpleasant-smelling decomposition products. In addition, the psyche changes the secretion of the emotionally sensitive apocrine sweat glands, so that fear, stress and sexual arousal become noticeable in terms of smell. The pill and pregnancy also affect body odor, especially locally on the nipples and in the genital area.
Copulins (female pheromones), the composition, concentration and smell of which change during the menstrual cycle, are found in women’s vaginal secretions. These are volatile short-chain, partly branched fatty acids, the smell of which causes an increase in testosterone levels in men on days when they are ready to conceive. Similarly, the female menstrual cycle synchronizes when women spend long periods of time together. Ultimately, choice of partner and sexuality as well as behavior in the family are largely unconsciously determined. The extent to which other pheromone-like substances are involved has not yet been clarified.
The intestinal flora has its share in body odor. This is most noticeable shortly after birth, when the intestinal flora changes from Lactobacillus bifidus to the later dominant Escherichia coli bacteria.

food

Worn textiles are an indicator of the volatile aromas that the skin emits into the environment. Meals hours ago can be recognized by their smell. The urine and excreted breath also have their own special notes. From a chemical point of view, they are low molecular weight substances that are retained in sweat and textile tissue or are excreted in the urine. Some are further broken down by the dermal microbiome and their smell intensified. Sulfur compounds and short-chain carboxylic acids dominate alongside amines, aldehydes, ketones and carboxylic acid esters.
A well-known example is this garlicaroma that is mainly formed from diallyl disulphide and diallyl trisulphide. Both sulfur compounds are excreted through the skin and the air we breathe. Various sulfur compounds are also used not only in the preparation of Onionsbut, as with garlic, are also released after eating. Since both types of vegetables are processed in a variety of ways, e.g. B. in sausages and spices, you can often smell their scent after meals. At the asparagus what is more affected is the urine, which contains thioacrylic acid S-methyl ester and 3- (methylthio) thiopropionic acid S-methyl ester with their characteristic scents shortly after eating. Both sulfur compounds are degradation products of aspartic acid (1,2-dithiolane-4-carboxylic acid). At radish and Cabbage Short-chain sulfur-containing compounds also enrich the breath. This also applies to many types of cheese that not only have a strong smell themselves, but are also unpleasant after consumption due to dimethyl disulfide and dimethyl trisulfide. Dimethyl sulfide is a constant companion of Seafood and in very low concentrations it even shapes the smell of the air above the sea. It arises, among other things, when algae break down by bacteria. Either Salt and fresh water fish in turn give off an ammonia-like odor in the urine, which is due to trimethylamine (see above). Likewise with fleshconsumption, especially of smoked products, has characteristic aromas on the skin and in the urine.

Smoke

Nicotine activates the body's own acetylcholine receptors. Vasoconstriction is triggered and the skin surface temperature is lowered. The skin becomes pale and sallow. In addition, enzymes such as matrix metalloproteinases are stimulated.1,2 In addition to proteases, esterases or other enzymes in the skin and dermal microbiome may also be affected. Our own observations suggest that individual components of cosmetic creams are subject to a rapid degradation process in smokers and produce objectively perceptible unpleasant odors on the skin. The subjectively changed olfactory sense of smokers does not play a role.

Pharmaceuticals

Active pharmaceutical ingredients can produce body odors in different ways:

  • The dryness of the mucous membranes in the mouth, nose and vagina is a side effect of pharmaceuticals. It changes the microflora and leads to unfamiliar smells.
  • The oral antibiotics used to treat infectious diseases disrupt not only the intestinal flora, but also the vaginal microflora. Spermicidal contraceptives such as gels, foams and suppositories also change the body's own balance and thus influence body odor.
  • In rare cases one can smell the breakdown products of medicinal products. Usually these are sulfur compounds. A particularly pungent garlic-like odor occurs on the skin after the application of ointments with dimethyl sulfoxide for the treatment of sports injuries and edema. The anti-inflammatory penetration enhancer is converted into gaseous dimethyl sulfide (thioether) and excreted through the skin. The gas is also produced in small quantities when cooking vegetables, especially cabbage.
Local body notes

Bad breath (Halitosis) is caused by bacteria that break down organic compounds and excrete volatile sulfur compounds such as hydrogen sulfide (digester gas). Causes can be dry mouth (see pharmaceuticals), food residues between the teeth or tongue coatings. The same applies to infections in the throat and esophagus

Foot odor: Under normal conditions, isovaleric acid predominates in the foot region. If special bacteria have colonized the skin of the feet, unpleasant-smelling sulfur-containing compounds can also develop, including mercaptans, thioethers and thioesters. Damp feet that tend to sweat promote these processes.

Genital region: The warm, humid environment of the vagina and vulva is an ideal field of activity for bacteria and fungi. It is true that the natural flora exudes an individual, typical body odor that is primarily not perceived as unpleasant. But disturbances in this area - often due to excessive hygiene - change the local microclimate and the secretions.

Cosmetics: If cosmetics are not scented, the natural smells of the individual components naturally appear on the skin. This means that the main function of perfumes, namely the covering of generally disruptive aromas, is missing. The body temperature of about 37 ° C (skin: 32-34 ° C) releases volatile components in particular after application, which can also come from accompanying substances of otherwise odorless substances. Their presence is pronounced in natural substances. So you can easily identify a shea butter or a vitamin A by its smell. The presence of highly unsaturated acids such as linoleic acid and alpha- and gamma-linolenic acid can already be recognized in ppb amounts by their breakdown products pentanal, hexanal and heptanal as well as the particularly odorous, unsaturated compounds 2-nonenal and 1-octen-3-one (1 ppb = part per billion = 0.000 000 001). Opinions also differ on inevitable natural odors such as algae and yeast extracts. What is dearly loved by some is completely rejected by others. Products with these natural extracts are not for sale in the Arab-Islamic world.
As already mentioned on the subject of smoking, the individual dermal microbiome can contribute to the fact that cosmetics produce different fragrances on the skin depending on the person. Because the microflora of the skin changes through cosmetic care. A remaining film of fats and hydrocarbons favors z. B. the proportion of anaerobic germs, while preservatives selectively or generally inhibit the growth of germs. Since the germ flora not only lives on components of the stratum corneum, but also breaks down cosmetic ingredients depending on their specialization, volatile breakdown products with different scents are created. The typical odor test that can be observed when trying out cosmetics also makes perfect sense for fragrance-free products. However, you should repeat the test a certain time after applying the product.

literature

  1. Lahmann C, Bergemann J, Harrison G, et al. Matrix metalloproteinase-1 and skin aging in smokers. Lancet 2001; 357: 935-936
  2. Sorensen LT, Zillmer R, Agren M, et al. Effect of smoking, abstention, and nicotine patch on epidermal healing and collagenase in skin transudate. Wound Repair Rain. 17 (3): 347-53 (2009)

Dr. Hans Lautenschläger