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Nanotechnology is a novel expanding area of research involved in manipulating properties and structures at nanoscale. Nanoparticles have recently received considerable attention in medical, biomedical, and biotechnological applications and have emerged in the fields of cosmetics and dermal preparations. This chapter introduces the cutting-edge science related to nanoparticles' role in the cosmeceutical industry. It starts by presenting skin structure and function. It then explains mechanisms of nanoparticle permeation through skin including transcellular, intercellular, and transappendageal pathways. Various ingredients used in beauty care products and their novel nanoformulations are discussed. A full discussion of the main nanoparticles that have been used in cosmetics is presented. The toxicity of nanoparticles, safety requisites for these products, and the regulation of nanoparticle applications in beauty care products are then described.

Air pollution is serious problem worldwide, especially in well-developed and industrialized countries. Much evidence exists on the relationship between air pollution and the development or exacerbation of cardiovascular and respiratory diseases; however, fewer studies concern the impact of air pollution and particulate matter on skin integrity. Studies suggest air pollutants such as tobacco smoke, concentrated air particles, volatile organic compounds, ozone, and NO 2 are significantly associated with an inflammatory response, weakened barrier function, and oxidative stress, which can lead to the development or exacerbation of inflammatory skin diseases, skin aging, as well as skin cancer. Topical application of antioxidants, tocopherol, aryl hydrocarbon receptor antagonists, as well as retinoids, can be used to buffer the harmful effects of free radicals and enhance the skin barrier, that is due to air pollutant interactions with the skin.

The interconversion of estrone (E1) and 17β-estradiol (E2) is catalyzed by 17β-hydroxysteroid dehydrogenase (17β-HSD) in peripheral steroidogenic organs such as the skin. To investigate gender differences of activity and skin distribution of 17β-HSD in human skin, enzymatic activity was measured in skin homogenates and skin horizontally sliced by 10 µm thickness in vitro. Reductive 17β-HSD (E2 formation from E1) in female skin has a lower substrate affinity than in male skin; Km (Michaelis-Menten constant) of female and male skin is 11.8 ± 6.5 and 2.0 ± 2.0 µM, respectively. Female skin had a tendency to activate estrogen; Vmax (maximum rate) for E2 formation, 5.8 ± 4.0 pmol/min/mg protein, is 1.7 times larger than E1 formation, 3.5 ± 1.5 pmol/min/mg protein, and, on the other hand, male skin tends to deactivate estrogen; Vmax for E1 and E2 is 10.5 ± 6.1 and 4.2 ± 3.7 pmol/min/mg protein, respectively. The concentration of metabolite had a peak value at 80–120 µm from the skin surface. Therefore, these in vitro results suggest that the enzymatic activities of 17β-HSDs have a gender difference in estrogen formation/metabolism and are distributed around the basement layer of the epidermis irrespective of sex. 17β-HSDs distributed around the basement epidermis may be effectively supplied with circulating estrogen from the papillary plexus to maintain the estrogen level in skin. This distribution pattern having a peak surrounding 100 µm from the skin surface indicates the importance for defense from noxae (e.g. detoxication) and maintenance of the internal environment (e.g. biosynthesis of hormones). Future studies should increase sample size and confirm these results by stricter statistical analysis.

Psoriasis is a chronic relapsing disease characterized by variable clinical features. Several factors may exacerbate its manifestations, or even trigger the disease, such as traumatic injury to the skin, physical and psychological stress, cold weather, excessive alcohol intake, and drugs such as lithium and beta-blockers. We describe the most common features of psoriasis and the exogenous factors that may induce, trigger or exacerbate the disease.

The chronic effects of the irritant sodium lauryl sulphate (SLS) on stratum corneum (SC) barrier function, determined by transepidermal water loss (TEWL) measurements and on epidermal cell kinetics, estimated by stratum corneum turnover time (SCTT) determination (dansyl chloride staining method), were investigated in 18 healthy female volunteers. SLS (7.5%) was applied without occlusion for 20 min once daily, over a period of 3 weeks (5 days a week) on dansyl chloride-stained skin and on untreated skin. SCTT of untreated skin (19.3 +/- 0.8 days; mean +/- SEM) was not changed by daily treatment with water (control) (19.3 +/- 2.0) but was significantly reduced by SLS (10.9 +/- 0.6; P less than or equal to 0.0001; compared to controls). However, TEWL was increased in SLS-treated sites 1.5-fold after 4 days of treatment (5.3 +/- 0.6 vs. 3.5 +/- 0.3; P less than 0.001). At the end of the second week, TEWL was increased 2.6-fold and after 3 weeks TEWL was 3.3 times higher than in controls 13.0 +/- 1.6 vs. 3.9, P less than or equal to 0.0001). The intensity of SLS-induced irritation as measured by TEWL was significantly correlated with baseline TEWL (r = 0.50; P less than or equal to 0.02) and significantly negatively correlated with SCTT of SLS treated sites (r = -50; P less than or equal to 0.02) but not with SCTT of untreated skin (r = 0.19).

'The purpose of this study is to determine the bioavailability of organic solvents following dermal exposures to contaminated soil and water. Breath analysis is being used to obtain real-time measurements of volatile organics in expired air following exposure in rats and humans. Rhesus monkeys will be used as surrogates for humans in benzene exposures. The exhaled breath data is being analyzed using physiologically based pharmacokinetic (PBPK) models to determine the dermal bioavailability of organic solvents under realistic exposure conditions. The end product of this research will be a tested framework for the rapid screening of real and potential exposures while simultaneously developing physiologically based pharmacokinetic (PBPK) models to comprehensively evaluate and compare exposures to organics from either contaminated soil or water. This report summarizes work 7 months into a 3-year project. Method development has produced systems for solvent exposure from soil and water which mimic actual exposure, and for which animals and human volunteers can be safely tested. Soil exposure is generally open to the air (working the soil) while water exposure is generally immersion. For 6--8 hour test exposure, a patch has been developed where soil is contained against the skin by a non-occlusive membrane, while simultaneously allowing volatilization of test solvent to the environment (activated charcoal). The water counterpart is an occlusive glass culture dish, sealed to skin with silicone adhesive. Shorter term exposure is done by one hand immersion in a bucket containing circulating water or soil, the volunteer instructed to move fingers through the water or soil. Human volunteers and animals breathe fresh air via a new breath-inlet system that allows for continuous real-time analysis of undiluted exhaled air. The air supply system is self-contained and separated from the exposure solvent-laden environment. The system uses a Teledyne 3DQ Discovery ion trap mass spectrometer (MS/MS) equipped with an atmospheric sampling glow discharge ionization source (ASGDI). The MS/MS system provides an appraisal of individual chemical components in the breath stream in the single-digit parts-per-billion (ppb) detectable range for each of the compounds proposed for study, while maintaining linearity of response over a wide dynamic range.'

SUMMARY Using a newly developed suction device, the mechanical properties of forearm and vulvar skin were studied in 22 healthy women, 12 before and 10 after the menopause. The ratio between viscous deformation (Uv) and elastic deformation (Ue) and the biological elasticity, i.e. the ratio between immediate recovery (Ur) and total deformation (Uf), were both significantly lower in vulvar than in forearm skin. Ur/Uf decreased significantly with load in vulvar, but not in forearm skin, whereas Uv/Ue was not load-dependent in either site. Uv/Ue remained constant with age in both test sites, whereas Ur/Uf was significantly lower in post-menopausal women in both forearm and vulvar skin. In vulvar, but not in forearm skin, Uv/Ue was significantly correlated with body height which may be an indicator of mechanical connective tissue properties. Viscous deformation plays a lesser role and biological elasticity is decreased in vulvar compared to forearm skin. Despite differences in mechanical parameters at both sites, age-related changes seem to be similar.

This prospective study (1977-1980) of cosmetic adverse reactions by eleven dermatologists identified 487 cases of cosmetic-induced dermatitis. Approximately half of the cases were covert in nature. Eighty percent were due to allergic contact dermatitis; the face, eye, and upper arm were the most involved sites. Skin care products, hair preparations (including colors), and facial makeup products were the most commonly involved product categories. Fragrances, preservatives, lanolin and lanolin derivatives, p -phenylenediamine, and propylene glycol were the most commonly identified causative agents. The data may not be representative of the country at large because of the special interests of the dermatologists involved.

A new animal test for evaluating the skin-irritant capacity of cosmetic and drug preparations and ingredients intended for repeated application is presented. The test is patterned on the 21-day occlusive test on man. Substances are applied 16 times (uncovered) to the skin of rabbits over a 3-wk period. The two parameters of the inflammatory response evaluated (16 times) throughout the test as indices of skin irritation are redness (cumulative irritation score) and fluid accumulation (changes in skinfold thickness). Measurements of these two parameters are highly correlated (r = 0·86; P < 0·001). Results on 60 test materials showed a significant correlation (r = 0·30; P < 0·02) between the cumulative irritation scores obtained on rabbits and those obtained on man. The usefulness and limitations of single-application (Draize type) and multiple-application tests for skin irritation are discussed. Exploratory results with hairless rats and hairless hamsters suggested that these species were not sufficiently responsive to be useful in skin-irritation studies. A radioimmunoassay of skin prostaglandin E disclosed no differences between irritated and control skin, suggesting that this technique cannot be used as an objective measure of skin irritation.

Human subjects were used to evaluate the skin sensitization potential of several substances used in marketed drugs and cosmetics, as well as other chemical agents. The results show that a modified Draize test is a useful, predictive patch-test procedure. Potentially strong sensitizers show a dose-response relationship when a range of concentrations of test material are used (at induction), whereas weak sensitizers may not; thus a range of concentrations of test materials may be used as a means of disclosing the potential of these compounds to produce delayed skin hypersensitivity.

Dimethyl thiophosphate (DMTP), one of the primary metabolites of azinphos-methyl, was measured in the urine of rats following dermal application of 100, 200 or 400 μg azinphos-methyl. A very strong correlation was found between the amount of pesticide applied and urinary DMTP levels. Using DMTP levels in urine following dermal and intramuscular (i.m.) dosing the percutaneous absorption was estimated to be approximately 60% of the applied dose. Increasing the dose from 100 to 400 μg/rat did not appreciably affect this. Percutaneous absorption was also determined using 14C ring-labeled azinphos-methyl and was found to be 91% of the applied dose. The underestimate by the DMTP method may be related to the lower sensitivity of the G.C. in determining the low levels of DMTP excretion which occurred for a number of days following dosing. Since absorption is calculated on the basis of total amount excreted, this could lead to the observed underestimate. The significant correlation between DMTP excretion and the amount of dermal exposure in rats is useful and has led to the initiation of studies in humans to establish whether a similar relationsip exists.

Studying age-related changes in the physiology, biochemistry, and molecular biology of isolated skin cell populations in culture has greatly expanded the understanding of the fundamental aspects of skin aging. The three main cell types that have been studied extensively with respect to cellular aging in vitro are dermal fibroblasts, epidermal keratinocytes, and melanocytes. Serial subcultivation of normal diploid skin cells can be performed only a limited number of times, and the emerging senescent phenotype can be categorized into structural, physiological, biochemical, and molecular phenotypes, which can be used as biomarkers of cellular aging in vitro. The rate and phenotype of aging are different in different cell types. There are both common features and specific features of aging of skin fibroblasts, keratinocytes, melanocytes, and other cell types. A progressive accumulation of damage in all types of macromolecules is a universal feature of cellular aging in all cell types. A progressive failure of molecular maintenance and repair pathways is the ultimate cause of cellular aging in vitro and in vivo.