Skin is the largest human organ, accounting for approximately 12-15% of body weight.1 Volatile organic compounds (VOCs) emanating from skin contribute to a person’s body odour, and may convey important information about metabolic processes. VOCs from skin derive from eccrine, sebaceous and apocrine gland secretions and their interactions with resident skin bacteria.2,3 These glands are distributed differently across the body; hence different regions of the body have different VOC profiles, and thus different odours.

Eccrine glands are found throughout the skin, but are especially concentrated in palms of hands, soles of feet, and the forehead. Eccrine sweat is mostly water, but contains glycoproteins (notably interleukin 1), lactic acid, sugars, amino acids and electrolytes.4

Sebaceous glands are concentrated on the upper part of the body.3 The upper chest, back, scalp, face and forehead may have as many as 400-900 sebaceous glands cm-2. Sebaceous gland secretions are rich in lipid materials such as cholesterol, cholesterol esters, long-chain fatty acids, squalene and triglycerides.3 These lipids provide substrate for growth and metabolism of skin microorganisms.

Apocrine glands are concentrated in the axillae, pubic area and areolas.2,4 Apocrine secretions are the chief source of underarm odorants (commonly known as ‘body odour’) and play a role in chemical signalling (for a review see Wysocki and Preti.5) Many previous studies have focused on VOCs emanating from the axillae, which reflect some contribution from all skin glands located in the axillae.6-10

VOCs from nonaxillary skin secretions have been studied as potential mosquito attractants,11-13 indicators of seasonal changes14 and ageing,15 and moderators of fragrances.16-19 It was recently demonstrated that skin emanations could be collected via rolling a stir-bar coated with polydimethylsiloxane across the arm with subsequent desorption and analysis by gas chromatography/mass spectrometry (GC/MS).20 Bernier et al.11-13 reported that hundreds of compounds canbe volatilized from skin secretions collected from the palms and backs of hands. Most of these compounds have been documented to be organic acids ranging in carbon size from C2 to C20. However, the most abundant (75-80%) organic acids found on skin are C16 and C18 saturated, monounsaturated and diunsaturated acids,12 which are not volatile at body temperatures.

In contrast, collection of skin VOCs using solid-phase microextraction (SPME) will collect low molecular weight compounds that are volatile at body temperature. SPME-GC/MS analyses of hand/wrist VOCs sampled in both winter and spring revealed 35 organic compounds.14 VOCs were reported to be more abundant in winter samples; however, the relative ratios of many (but not all) of the compounds did not vary between seasons. This observation led the authors to speculate that the moist spring air allowed the skin to harbour more bacteria that hydrolysed and decomposed some of the VOCs.

A study of male Japanese subjects used T-shirts worn for 3 days to collect skin odours. VOCs emanating from rectangular pieces cut from the backs of these T-shirts were studied.15 The authors suggested that skin secretions in men older than age 39 years contain larger amounts of unsaturated aldehydes than secretions from younger men. These compounds, particularly 2-nonenal, were reported to impart an unpleasant ‘ageing odour’ to older Japanese men.

Most acids, alcohols and aldehydes found in skin secretions apparently originate from the interactions between sebaceous gland secretions and cutaneous bacteria.12,21 Anaerobic bacteria living in the hair follicle/sebaceous gland duct use lipases to liberate long-chain acids from triglycerides, which are further metabolized by aerobic bacteria into longer, saturated and unsaturated acids and smaller volatile acids, aldehydes and alcohols.21

Other potential sources of skin volatiles are putative odorants carried by the apocrine secretion odour-binding protein (ASOB) 1.22 This protein might bind odorous acids that can be liberated by interaction with cutaneous bacteria. A previous study demonstrated that this protein does carry odorants in the underarm, and is present in sebaceous-rich perspiration from the forehead.22

Tracking dogs trained to recognize an individual’s scent on garments from a particular body part (e.g. chest, arm, leg) are not reliably able to generalize the individual’s odour to other body parts, suggesting that a different odorant milieu may characterize the back and forearm (for a review see Jenkins23). In this study, we performed a comprehensive analysis of VOCs from the upper back and forearm of 25 healthy subjects using two complementary sampling techniques, SPME and solvent extraction. Skin secretions from the back of each subject also were analysed for the presence of the potential VOC carrier ASOB1.

The goals of the study were: (i) to identify VOCs emanating from the upper back and forearm skin; (ii) to determine whether VOCs vary in a qualitative or quantitative manner; and (iii) to determine if VOCs vary in relative abundance with gender, age or locus, i.e. back and forearm. The upper back and forearm were chosen because they are easily accessible with minimal inconvenience to subjects. In addition, these body regions differ with respect to density of sebaceous glands (upper back > forearm) and skin bacteria, as well as exposure to sun, environment and consumer products.3,21

Analyses of volatile organic compounds from human skin.

Individuals are thought to have their own distinctive scent, analogous to a signature or fingerprint. To test this idea, we collected axillary sweat, urine and saliva from 197 adults from a village in the Austrian Alps, taking five sweat samples per subject over 10 weeks using a novel skin sampling device. We analysed samples using stir bar sorptive extraction in connection with thermal desorption gas chromatograph–mass spectrometry (GC–MS), and then we statistically analysed the chromatographic profiles using pattern recognition techniques. We found more volatile compounds in axillary sweat than in urine or saliva, and among these we found 373 peaks that were consistent over time (detected in four out of five samples per individual). Among these candidate compounds, we found individually distinct and reproducible GC–MS fingerprints, a reproducible difference between the sexes, and we identified the chemical structures of 44 individual and 12 gender-specific volatile compounds. These individual compounds provide candidates for major histocompatibility complex and other genetically determined odours. This is the first study on human axillary odour to sample a large number of subjects, and our findings are relevant to understanding the chemical nature of human odour, and efforts to design electronic sensors (e-nose) for biometric fingerprinting and disease diagnoses.

/pdf/individual-and-gender-fingerprints-in-human-body-odour-32kz9kj425.pdf

Individual and gender fingerprints in human body odour

We evaluated the volatile organic compounds (VOCs) present in human odor by using headspace solid phase microextraction gas chromatography-mass spectrometry for the extraction, separation, and analysis of the collected samples. Volatile organic compounds present in the headspace above axillary sweat samples collected from different individuals showed the presence of various types of compounds including organic fatty acids, ketones, aldehydes, esters, and alcohols. Qualitative differences and similarities noted between the males and females studied along with differences in chemical ratio patterns among the common compounds demonstrated the ability to differentiate between individuals through the examination of VOCs.

http://forensicentomologist.com/wp-content/uploads/2008/05/211.pdf

Comparison of the volatile organic compounds present in human odor using SPME-GC/MS.

Odors emitted by human skin are of great interest to biologists in many fields; applications range from forensic studies to diagnostic tools, the design of perfumes and deodorants, and the ecology of blood-sucking insect vectors of human disease. Numerous studies have investigated the chemical composition of skin odors, and various sampling methods have been used for this purpose. The literature shows that the chemical profile of skin volatiles varies greatly among studies, and the use of different sampling procedures is probably responsible for some of these variations. To our knowledge, this is the first review focused on human skin volatile compounds. We detail the different sampling techniques, each with its own set of advantages and disadvantages, which have been used for the collection of skin odors from different parts of the human body. We present the main skin volatile compounds found in these studies, with particular emphasis on the most frequently studied body regions, axillae, hands, and feet. We propose future directions for promising experimental studies on odors from human skin, particularly in relation to the chemical ecology of blood-sucking insects.

Human skin volatiles: a review

Characterization of the volatile organic compounds present in the headspace of decomposing human remains.

Study and identification of volatile compounds from human skin

The present invention relates to a topical composition comprising a malodor-reducing effective amount of a rosemary extract, or active fraction thereof, in combination with a self-tanning effective amount of DHA The invention also provides a method of reducing the potential for malodor generation of a DHA composition comprising adding to the composition an effective amount of rosemary extract or active fraction thereof

Cosmetic compositions containing rosemary extract and dha

A new test method has been developed to determine surface energy of hair fibers through measurements of contact angles at two hair/liquid interfaces. By measuring changes in surface energy of the same hair fiber before and after a cosmetic treatment, effects of active ingredients and the performance of tested formulations can be evaluated.The establishment of the method is based on Fowkes theory (1,2) described with two components, a dispersive and a non-dispersive component. The non-polar liquid used in this study was diiodomethane, and the polar liquid was benzyl alcohol. A Kruss 100 Tensiometer was used to measure contact angles of hair fibers. Virgin dark brown and regular bleached hairs were treated with selected conditioner formulations. Reductions in combing forces of hair tresses before and after respective treatments were correlated with decreases in average surface energy of hair fibers obtained from the corresponding tresses.Experimental results indicate that the average surface energy of hair fibers treated with conditioners decreases and the hydrophobicity of the hair surface increases, the results correlate well with the reduction in combing forces after respective treatments. This research work provides a new methodology to evaluate/screen conditioning performance of hair care ingredients and formulations for development of better products.

Peter A. Landa

Papers

Study and identification of volatile compounds from human skin

Cosmetic compositions containing rosemary extract and dha

Study of hair surface energy and conditioning.