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PubMed1999

Human skin surface lipid film: an ultrastructural study and interaction with corneocytes and intercellular lipid lamellae of the stratum corneum.

Sebum is a complex mixture of lipids, which is secreted by mammalian sebaceous glands, and forms a fluid film over the skin surface. After sebum is secreted, it becomes mixed with lipid from the keratinizing epithelium and forms the skin surface lipid film (SSLF). Until now, direct fine structural observation of the SSLF has been lacking. In the present work, we viewed the detailed structures of the human SSLF by ruthenium tetroxide staining. The results showed that the SSLF formed an amorphous sheet of variable thickness on the skin surface instead of forming lipid droplets, as had been the usual assumption. In general, its thickness was < 0.5 microm or even negligible in sebum-poor extremities. However, in the sebum-rich face, its thickness was > 4 microm in focal areas. Consistent with the thickness of SSLF, the sebum quantity showed great regional variation. It varied from 1 microg/cm2 (leg) to 189 +/- 42.7 microg/cm2 (mean +/- SD: face). The SSLF was composed of numerous fine granules of about 4-5 nm in a random orientation. Within the SSLF, variable amounts of deranged lipid lamellae derived from corneocytes were mixed with sebum. As well as on the skin surface, a similar amount of sebum was also found between the desquamating corneocytes in the uppermost several layers of the stratum corneum (SC). We also observed the presence of intercellular lipid lamellae in the outer layers of the SC: their lipid envelope remained intact even in desquamated corneocytes. Our results provide some new insights concerning the structure of the SSLF and its relationship with the SC.

Adult↗
PubMed1986

Effect of cyproterone acetate-ethinyl estradiol treatment on the proportions of linoleic and sebaleic acids in various skin surface lipid classes.

The effect of high-dose cyproterone acetate-ethinyl estradiol treatment on rates of sebum secretion and on the proportions of linoleic acid (18:2 delta 9,12) and sebaleic acid (18:2 delta 5,8) in the skin surface lipids of three female acne patients was examined. Changes in rates of sebum secretion were evaluated indirectly by measuring the ratio of wax esters/(cholesterol + cholesterol esters) in the subjects' skin surface lipid. In two of the subjects, this ratio indicated a reduction of sebum secretion rates to the childhood range. Concomitantly, there was an increase in linoleic acid and a decrease in sebaleic acid in all lipid classes. In the third subject, in whom there was only a small reduction in sebum secretion rate, the proportion of linoleic acid in the cholesterol esters more than doubled, but the changes in the other lipid classes were small or nonexistent. The results indicate that the proportions of linoleic acid and sebaleic acid in sebum are influenced by sebum secretion rates.

Acne Vulgaris↗
PubMedDate not supplied

Acne and sebaceous gland function.

The embryologic development of the human sebaceous gland is closely related to the differentiation of the hair follicle and the epidermis. The number of sebaceous glands remains approximately the same throughout life, whereas their size tends to increase with age. The development and function of the sebaceous gland in the fetal and neonatal periods appear to be regulated by maternal androgens and by endogenous steroid synthesis, as well as by other morphogens. The most apparent function of the glands is to excrete sebum. A strong increase in sebum excretion occurs a few hours after birth; this peaks during the first week and slowly subsides thereafter. A new rise takes place at about age 9 years with adrenarche and continues up to age 17 years, when the adult level is reached. The sebaceous gland is an important formation site of active androgens. Androgens are well known for their effects on sebum excretion, whereas terminal sebocyte differentiation is assisted by peroxisome proliferator-activated receptor ligands. Estrogens, glucocorticoids, and prolactin also influence sebaceous gland function. In addition, stress-sensing cutaneous signals lead to the production and release of corticotrophin-releasing hormone from dermal nerves and sebocytes with subsequent dose-dependent regulation of sebaceous nonpolar lipids. Among other lipid fractions, sebaceous glands have been shown to synthesize considerable amounts of free fatty acids without exogenous influence. Sebaceous lipids are responsible for the three-dimensional skin surface lipid organization. Contributing to the integrity of the skin barrier. They also exhibit strong innate antimicrobial activity, transport antioxidants to the skin surface, and express proinflammatory and anti-inflammatory properties. Acne in childhood has been suggested to be strongly associated with the development of severe acne during adolescence. Increased sebum excretion is a major factor in the pathophysiology of acne vulgaris. Other sebaceous gland functions are also associated with the development of acne, including sebaceous proinflammatory lipids; different cytokines produced locally; periglandular peptides and neuropeptides, such as corticotrophin-releasing hormone, which is produced by sebocytes; and substance P, which is expressed in the nerve endings at the vicinity of healthy-looking glands of acne patients. Current data indicate that acne vulgaris may be a primary inflammatory disease. Future drugs developed to treat acne not only should reduce sebum production and Propionibacterium acnes populations, but also should be targeted to reduce proinflammatory lipids in sebum, down-regulate proinflammatory signals in the pilosebaceous unit, and inhibit leukotriene B(4)-induced accumulation of inflammatory cells. They should also influence peroxisome proliferator-activated receptor regulation. Isotretinoin is still the most active available drug for the treatment of severe acne.

Acne Vulgaris↗
PubMed2003

[Normal and pathologic sebaceous function. Research in a shallow milieu?].

Modern therapeutic approaches allow to control sebaceous secretion but knowledge about the sebaceous gland and its precise function within the pilosebaceous unit is still insufficient. Steroid hormones are the principal albeit not exclusive regulators of the sebaceous glands. Three phases may be distinguished in sebaceous physiology: secretion-production, stocking in the follicular reservoir, and excretion. Human "native" intracellular sebum, before secretion, is composed of squalene, waxes, and triglycerides. Once secreted, the sebum is colonised by various xenobiots whose development is controlled by several defensive humoral mechanisms and by the contact with ambient oxygen. Oxygen and micro-organisms transform "native" sebum, lysis of triglycerides to fatty acids being the most pronounced activity. Certain components of this complex mixture of molecules present in the sebum are clearly cytotoxic or irritant, provoking reactive follicular hyperkeratosis and comedone formation--the first step to acne. Some lipophilic organisms like Malassezia yeast may be highly antigenic and induce chronic inflammatory reactions like in seborrhoeic dermatitis. Demodex is an inrafollicular parasite feeding on sebum that frequently causes blepharitis. Sebum is also a vehicle transporting and transmitting several endogenous and exogenous molecules, including potential regulatory factors of hair follicles. Recent development of in vitro cultures of functional sebocytes should help to better understand several aspects of the sebaceous gland's biology.

Acne Vulgaris↗
PubMed2006

Investigation of the skin characteristics in patients with severe GH deficiency and the effects of 6 months of GH replacement therapy: a randomized placebo controlled study.

OBJECTIVE: The presence of GH receptor in human skin and its appendages suggests a direct effect of GH on skin characteristics. The skin is usually thin and dry in patients with GH deficiency (GHD). Sheehan's syndrome classically refers to postpartum hypopituitarism and GH is one of the earliest pituitary hormones lost. While severe GHD is a well-established feature of Sheehan's Syndrome, skin characteristics and the effects of GH replacement therapy (GHRT) have been investigated neither in Sheehan's syndrome nor in other disorders of GHD. The aim of this study was to investigate the skin characteristics, including the sebum content, hydration (skin capacitance), transepidermal water loss (TEWL), pH and skin temperature, and particularly the effects of 6 months of GHRT on these parameters in GH deficient patients with Sheehan's syndrome. PATIENTS AND DESIGN: Sixteen severely GH deficient women with Sheehan's syndrome (48.1 +/- 10.9 years), and 20 age and menopausal status similar women as control subjects were included. Ten patients received recombinant GH for 6 months (treatment group) and 6 patients received placebo (placebo group) during this period. Skin properties were measured at baseline and after 6 months of GHRT using noninvasive and well-established measuring methods. RESULTS: At baseline the skin capacitance was significantly decreased on the forehead and forearm, and sebum content was significantly decreased on forehead in patients with Sheehan's syndrome compared to control subjects (P < 0.05). In the treatment group there was a significant increase in sebum content on forehead after 6 months of GHRT compared to the baseline value (P < 0.05). However there were no significant changes in other parameters including sebum content on the forearm, TEWL, Ph, skin capacitance and temperature of both the forearm and forehead. In the placebo group there were no changes in any of the evaluated parameters after 6 months of treatment compared to baseline values. CONCLUSIONS: The present study clearly shows that the sebum content on the forehead and skin hydration of the forehead and forearm are significantly decreased in GH deficient patients with Sheehan's syndrome. However 6 months of GHRT significantly increased only the sebum content on the forehead. These data suggest that GH and/or IGF-I may have a modulatory role on several skin characteristics.

Adult↗
PubMed1989

Responses of tsetse flies (Glossina spp.) to compounds on the skin surface of an ox: a laboratory study.

The behaviour of male Glossina morsitans morsitans Westwood and Glossina pallidipes Austen (Diptera: Glossinidae) alighting on targets with or without ox sebum was compared. The presence of ox sebum did not increase significantly the number of flies alighting on the target in either species. However, after contact with the sebum coated target, both species showed an increase in flight activity, and G. m.morsitans showed a greater tendency to return to the target. This behaviour resulted in a number of short flights which may reflect the search for a feeding site on a host. The duration of each visit to the target was significantly reduced when sebum was present for G. m. morsitans but not for G. pallidipes. This is explained by documented differences in the resting behaviour of the two species which shows that G. m. morsitans normally rests for longer periods on the surface of an untreated black target than does G. pallidipes. Other experiments showed that the presence of sebum elicited a probing response in G. m. morsitans and G. pallidipes. The results are discussed with reference to the possible use of host sebum to improve trap catches in the field.

Animals↗
PubMed1995

Field studies on the effect of cattle skin secretion on the behaviour of tsetse.

The effect of ox skin secretions (sebum) on the behaviour of tsetse flies, Glossina spp., was investigated in the field using electrified targets, some of which operated intermittently, and by direct observations of flies landing on treated and untreated cloth. As the off-period of an intermittently operating electrified target increased, the catch decreased both with and without the sebum present. Targets with sebum always caught more flies than targets without sebum, but there was no evidence to suggest that sebum increased the duration of stay on a target. Direct observations of flies on cloth targets revealed that for both species the presence of sebum reduced the duration of contact and for G.pallidipes the number of return contacts was increased. The results from direct observations were used to predict the number of repeat landings that would need to be made by flies in order to account for the catch of tsetse at intermittently electrified targets.

Animals↗
PubMed1997

The effects of hair density of beef cattle on Haematobia irritans horn fly populations.

We show the relationships that exist between the amount of hair and quantity of sebum on cattle skin and the population density of the horn fly, Haematobia irritans. Brahman and Chianina steers had means of 2390 and 1587 hairs per cm2, respectively, significantly more than the mean number of hairs on Angus, Brahman x Angus Crossbred, Charolais, and Red Poll steers. The Chianina steers had > 30% more sebum present on their skin and hair (0.58g/929 cm2) than the Angus, Charolais, and Red Poll steers at the Beef Cattle Research Station Savoy, Arkansas. The Brahman steers had a significantly greater amount of sebum present on the skin (1.51 g/929 cm2) than the Crossbred and purebred Angus steers (0.55 and 0.25 g/929 cm2, respectively) at the South Central Family Farms Research Centre Booneville, Arkansas. The Brahman and Chianina steers had means of 61.9 and 17.0 horn flies per steer, respectively, during the fly season, whereas the Angus, Crossbred, Charolais and Red Poll steers had fly season means that ranged from 76.9 to 265.8 flies per steer. Regression analysis showed that an increase of 100 hairs per cm2, was associated with a reduction of 11 horn flies in the Angus II, 5 in Angus I, 20 in Charolais, 37 in Red Poll, and 0.4 in Chianina steers at the Savoy Station and a reduction of 6.6 horn flies for the Angus, Brahman, and Crossbred steers at the Booneville Centre. Regardless of cattle breed, an increase of 1.0 g of sebum per 929 cm2 output by the steer was associated with 478.5 additional hairs per cm2 on the animal. Each increase of 0.25 g of sebum per 929 cm2 resulted in a decrease of 9.2 horn flies per steer. We conclude that some of the factors responsible for fly-resistance in cattle are hair density and the corresponding amount of sebum present on cattle skin and hair.

Animals↗
PubMed1988

[Quantification of sebaceous excretion in volunteers: influence of chronological age, sex and race].

The "sebum" secretion was evaluated in caucasian, black, yellow and mullato people of different ages by the osmic acid technique utilizing a semi-quantitative scale of score ranging from 0 to 9 points. The results have shown: 1) there is significant difference between to "sebum" secretion (CL = casual level or SER = sebum excretion rate) of males and females greater than or equal to 60 years old, regardless the race; 2) males and females of each age subgroup have shown no difference of "sebum" secretion (NC or TRE) regardless the race; 3) male volunteers of different races have shown no difference secretion regardless the age and the race. On the other hand, females greater than or equal to 60 years old, regardless the race have shown low "sebum" secretion tham of 15-19 and 50-59 years old; 4) no circadian, ultradian and seasonal rhythm of "sebum" secretion were verified.

Adolescent↗
PubMed1986

Dilutional effect of increased sebaceous gland activity on the proportion of linoleic acid in sebaceous wax esters and in epidermal acylceramides.

Sebaceous wax esters and epidermal acylceramides were isolated from skin surface lipid obtained from children and from young adults. Fatty acid methyl esters (FAME) were prepared from the esterified fatty acids of these lipid classes and analyzed to ascertain the proportions of methyl linoleate (18:2 delta 9,12), methyl sebaleate (18:2 delta 5,8), and methyl sapienate (16:1 delta 6). On the same subjects, 2 measures of sebum secretion rate were obtained, namely the sustainable wax ester secretion rate (WESR) on the forehead and the ratio of wax esters/(cholesterol + cholesterol esters) [WE/(CH + CE)] in the surface lipid. The proportions of methyl linoleate in FAME from the wax esters decreased, and the proportions of methyl sebaleate increased, with increased rates of sebum secretion. For both methyl linoleate and methyl sebaleate, a better correlation was obtained when the ratio of WE/(CH + CE) was used as a measure of sebum secretion rather than the WESR. The proportions of methyl linoleate in the FAME from the acylceramides were also inversely related to ratios of WE/(CH + CE). In acylceramides, linoleate was replaced by sapienate, a major fatty acid of human sebum. It appears, therefore, that sebum fatty acid composition may change with changes in sebaceous gland activity, and that sebum fatty acids can enter the epidermis and be incorporated into epidermal lipids.

Acne Vulgaris↗
PubMed2005

Effect of chlorophyllin-chitosan on excretion of dioxins in a healthy man.

We investigated the usefulness of chitosan and chlorophyllin-chitosan (chl-chitosan) administration for reduction of the body burden of environmental dioxins, including polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/ Fs) and coplanar polychlorinated biphenyls (Co-PCBs), by examining the excretion levels in the feces and sebum of a healthy man. The volunteer ate the same three meals every day during the 40-d experiment, which was composed of five phases (I-V) of 8 d each. In phase I (days 1-8), the volunteer was given only the basal diet. In phases II-V, 0.2 g of chitosan, 0.6 g of chitosan, 0.2 g of chl-chitosan, and 0.6 g of chl-chitosan, respectively, were administered immediately after each meal. We measured daily the amount of dioxins occurring in the feces and sebum during the last 5 d of each phase. The total toxicity equivalency (TEQ) of the dioxin in phases I-V were 27, 26, 38, 36, and 67 pg/d in the feces and 20, 19, 16, 16, and 14 pg/d in the sebum, compared with 74 pg/d in the food. The excretion of dioxins in the feces was significantly increased in phases III, IV, and V, being 140% (p < 0.05), 135% (p < 0.05), and 249% (p < 0.01) of the control level (phase I). Although the dioxin in the sebum was slightly decreased in phase V as compared with the control level, the total amount of excreted dioxin in feces and sebum was increased significantly in phase V, being 174% of the control level, which is almost the same level as that in the food. This indicates that chl-chitosan can prevent accumulation of dioxin, at least at the intake level of normal foods.

Chitosan↗
PubMed1997

Correlation of clinical, endocrine and molecular abnormalities with in vivo responses to high-dose testosterone in patients with partial androgen insensitivity syndrome.

OBJECTIVE: To investigate the responses of two patients previously diagnosed as Reifenstein's syndrome to graded high-dose testosterone in terms of hormone levels, nitrogen balance and sebum secretion and to attempt to correlate these parameters with the properties of their androgen receptors and mutations in the androgen receptor gene. DESIGN: Nitrogen balance was determined by comparing controlled nitrogen intake to the amount excreted. Sebum excretion was measured on the forehead. Patients were studied during control periods (no treatment) and during administration of testosterone propionate. Blood samples were used as a source of genomic DNA and to measure peripheral hormone levels; androgen receptor binding was determined using genital skin fibroblasts. PATIENTS: Two patients of XY karyotype, with ambiguous external genitalia and problems of testicular descent who had required mastectomy as teenagers. Normal male controls of proven fertility. MEASUREMENTS: Nitrogen balance, sebum excretion rate and peripheral hormone levels (testosterone, dihydrotestosterone, LH and FSH) were studied before and after testosterone therapy (1 or 5 mg/kg/day). Genomic DNA was extracted from peripheral blood leucocytes and regions of the androgen receptor gene amplified by polymerase chain reaction using pairs of specific primers. Mobility of amplified DNA from patients was analysed on denaturing gradient acrylamide gels and fragments differing in mobility from those of normal controls were sequenced. Fibroblasts were cultured from scrotal skin biopsies and androgen receptor binding parameters, subcellular localization and up-regulation were determined. RESULTS: Testosterone therapy resulted in raised plasma testosterone, dihydrotestosterone and oestradiol in both patients. In patient 1 (lesser genital abnormality), LH was suppressed by 5 mg/kg/day testosterone to the upper limit of the normal range but FSH remained low normal. Both LH and FSH were suppressed by testosterone treatment in patient 2 (greater genital abnormality). Nitrogen retention was increased in both patients (4.2 and 3.0 g/24 h respectively); sebum excretion rate increased to normal in patient 1 but showed no change in patient 2. Mutations in the androgen receptor gene were identified in both patients. In patient 1 a single nucleotide change from adenosine to guanosine resulted in the substitution of glycine for glutamic acid at position 772 within the hormone binding domain of the receptor. In patient 2 a single nucleotide mutation from guanosine to adenosine resulted in the substitution of lysine for arginine at position 608 (exon 3) situated in the second zinc finger of the DNA binding domain. Both patients had a normal number of androgen binding sites in genital skin fibroblasts but those in patient 1 showed reduced binding affinity and rapid dissociation of receptor/ligand complexes while those in patient 2 showed defective nuclear localization. CONCLUSION: In patients with partial androgen insensitivity syndrome the type of androgen receptor mutation and responses to short-term androgen treatment can be correlated with the individual's potential to virilize. If there is a mutation in the androgen receptor DNA binding domain the patient may show little ability to virilize either spontaneously at puberty or after androgen treatment. Sebum excretion appears to be more discriminating than nitrogen balance or gonadotrophin suppression as an index of tissue response to androgens.

Adult↗
PubMed1987

Skin lipids: an update.

The stratum corneum lipids, responsible for the epidermal water barrier, consist principally of ceramides, cholesterol, cholesteryl sulfate, and free fatty acids. These lipids are arranged in multiple intercellular lamellae that provide an efficient water barrier because of the crystalline array of the straight and predominantly saturated lipid chains. Interlamellar linkages provided by lipids based on 30-carbon omega-hydroxyacids may be responsible for holding together the intercellular lamellae as well as for assembly of the lamellar granules of the granular cells. The normally ordered exfoliation of corneocytes as they arrive at the surface seems to require hydrolysis of the cholesteryl sulfate to free cholesterol. The sebaceous glands secrete continuously, producing sebum that consists predominantly of triglycerides, wax esters, and squalene. High rates of sebum production per sebocyte result in low levels of linoleate in the sebaceous esters, subjecting the follicular epithelium to essential fatty acid deficiency and the characteristic hyperkeratosis that results in comedo formation. Suppression of sebum production by drugs elevates sebum linoleate concentration and relieves follicular hyperkeratosis. Thus, sebum continues to be a prime suspect in the crime of acne. Low levels of sebaceous gland activity are not correlated with the occurrence of dry skin.

Acne Vulgaris↗
PubMed1987

Functional blockage of open comedones.

Sebum excretion rate was measured by a photometric technique. We demonstrated a high correlation between sebum excretion rates on the left and right sides of the upper back and between back and forehead skin. Sebum excretion rate measurements overlying an open comedone (blackhead) were significantly lower than those obtained from normal skin. This observation demonstrates a functional obstruction to the outflow of sebum and would suggest that the lack of involvement of open comedones in inflammatory acne is not because of the maintenance of a free flow of sebum.

Acne Vulgaris↗
PubMed1976

Effect of alpha-melanocyte-stimulating hormone and testosterone on cutaneous and modified sebaceous glands in the rat.

The effects of alpha-MSH and testosterone propionate on sebum secretion, sebaceous gland volume, dermal lipogenesis, and preputial gland weight and lipogenesis were examined in hypophysectomized rats. Hypophysectomy reduced sebum secretion, sebaceous and preputial gland size, and dermal and preputial gland lipogenesis. The greatest effects were seen on the biosynthesis of wax esters and squalene. Testosterone propionate (TP) increased sebum secretion, sebaceous gland volume and preputial gland weight and lipogenic activity, but had no significant effect on the pattern of lipid labelling. alpha-MSH had no effect on sebaceous or preputial gland size, but increased sebum secretion and dermal lipogenesis, especially wax ester biosynthesis. When given together TP and alpha-MSH had a synergistic effect on sebum secretion and on dermal and preputial gland lipogenesis, and the pattern of lipid labelling was shifted towards normal. TP and alpha-MSH also showed synergism in increasing preputial gland weight, but together they had no greater effect on sebaceous gland volume than that achieved with TP alone. These results suggest that TP and alpha-MSH have different actions on the sebaceous glands with alpha-MSH acting predominantly on lipogenesis and TP on cellualr proliferation and turnover leading to an increase in gland size. Preputial glands differ from cutaneous sebaceous glands in their response to alpha-MSH and androgen which could be a reflection of their more specilized function.

Animals↗
PubMed2003

[Effect of topical retinoid therapy on seborrhea using iontophoresis].

Increased sebum production is one of causes of Acne. This is under androgen control. Acne subjects have significantly greater sebum production than subjects without Acne and this relates to Acne's severity. Reduction in sebum production is associated with improvement in Acne and it can realize with anti-androgen therapy and isotretinoin therapy. But these therapies can not keep away from systematically influence. Topical retinoids do not affect sebum production and approximately 80% of tretinoin applied remains on the skin surface. Iontophoresis offer methods for enhancing the percutaneous absorption of drugs and increase of drug concentration in skin. The aim of the study was to establish possibility of improvement retinoin efficacy by iontophoresis. Our results show that application of tretinoin by iontophoresis do not affect on sebum production.

Acne Vulgaris↗
PubMedDate not supplied

Deposition of salicylic acid into hamster sebaceous.

In an earlier paper, we identified vehicles that are miscible with sebum, using differential scanning calorimetry (DSC). In this paper, the potential of these vehicles to deliver salicylic acid (SA) into the sebum-filled follicles of hamster ears is examined. The main objective of this study is to correlate the melting transitions of a model sebum with the follicular delivery of SA, using two different types of vehicles (fatty and polar). Generally, the fatty vehicles show higher deposition than the polar vehicles. Follicular delivery of salicylic acid correlates well with its solubility in the respective vehicles. This extent of deposition also shows a relationship with the effect of the vehicle on thermal behavior of the model sebum. The nature of the relationship depends on the vehicle (polar or fatty) tested. We conclude that DSC could be used to identify appropriate vehicles for drugs whose follicular delivery depends on solubility. The results also suggest that delivery into the sebaceous glands occurs by two different mechanisms, depending upon the polarity of the vehicle and the physicochemical properties of the drug. The results of these experiments are further extended to investigate follicular delivery of SA from two different types of oil-in-water emulsion formulations. From these studies we conclude that either increasing the volume of the oil phase or changing the emulsion to a water-in-oil emulsion would increase follicular deposition. Our research highlights the role of sebum, its compatibility with drug molecules, and vehicle selection in the transport of drugs into the follicles. The overall results of these experiments provide a reasonable understanding of the mechanisms underlying the transport of drugs to, and subsequently through, the sebaceous follicle.

Animals↗
PubMedDate not supplied

Microemulsions of triglyceride-based oils: The effect of co-oil and salinity on phase diagrams.

Microemulsification of triglyceride-based oil is challenging due to the formation of undesirable phases such as macroemulsions, liquid crystals, or sponge phases. This research evaluates the formation of artificial sebum microemulsions using linker molecules, with the addition of co-oil to help enhance sebum solubilization. The microemulsion consists of a lipophilic linker (sorbitan monooleate), a hydrophilic linker (hexylglucocide), a main surfactant (sodium dioctyl sulfosuccinate), a co-oil, and artificial sebum. The effect of adding co-oil to the phase behavior and the microstructure of the resulting microemulsion is described. The effect of several types of co-oil is also studied; the co-oils evaluated here are squalene, squalane, isopropyl myristate, and ethyl laurate. The effect of salinity on the microemulsion phase behavior is also presented. Fish diagrams are obtained by plotting total surfactant/linker concentration as a function of sebum fraction in the oil mixture (co-oil + sebum). Different microemulsion types (Winsor Types I, II, III, and IV) are formed, depending on the total surfactant/linker concentration and the fraction of co-oil in the oil mixture. Winsor Type IV (single-phase) microemulsions are observed at high surfactant/linker concentrations. These single-phase, isotropic, and low-viscous fluids are particularly useful for cleansing and delivery of functional ingredients in skin care products. Salt addition shifts the fish diagram towards more hydrophobic oil systems and higher surfactant/linker concentrations.

Cosmetics↗