Skin moisture

The guarded hot-plate method can be modified to perform dry and wet heat transfer testing (sweating skin model). Some plates contain simulated sweat glands and use a pumping mechanism to deUver water to the plate surface. Thermal comfort properties that can be deterrnined from this test are do, permeabihty index (/ ), and comfort limits. PermeabiUty index indicates moisture—heat permeabiUty through the fabric on a scale of 0 (completely impermeable) to 1 (completely permeable). This parameter indicates the effect of skin moisture on heat loss. Comfort limits are the predicted metaboHc activity levels that may be sustained while maintaining body thermal comfort in the test environment. 

The smoothing or emoUient properties of creams and lotions are critical for making these emulsions the preferred vehicles for facial skin moisturizers, skin protectants, and rejuvenating products. On the body, emoUients provide smoothness and tend to reduce the sensation of tightness commonly associated with dryness and loss of Hpids from the skin. Although a wide variety of plant and animal extracts have been claimed to impart skin benefits, vaUd scientific evidence for efficacy has been provided only rarely. 

Humans seek and want thermal comfort, even at work in industrial settings. Clothing, activities, posture, location, and shelter are chosen, adjusted, altered, and sought consciously and unconsciously to reduce discomforts and enable us to focus more on the other tasks of life. Discomfort can contribute to mistakes, productivity decreases, and industrial accidents. " Thermal discomfort results from the physiological strain of thermoregulation. The strain can be in the form of altered body temperatures, sweating and excessive skin moisture, muscle tension and stiffness, shivering, and loss of dexterity. A small... 

HOT Tblood flow to. skin (vasodilation), heart rate T, sweating T, skin moisture T, body temperatures T, metabolism T... 

Some of the discomfort of warm environments, the perception of skin moisture, and the interactions of clothing fabrics with the skin may be due to the moisture itself. The skin s outer layer of dead squamous cells of the stratum corneum can readily absorb or lose water. With moisture addition, the cells swell and soften. With drying, they shrink and become hard. In this setting the skin s moisture may be better indicated or characterized by the relative humidity of the skin (RH i ) rather than skin wettedness,-" ... 

As mentioned previously, the other term for characterizing skin moisture is skin wettedness (w) or the size of the water film as a fraction of total skin area that is necessary to account for the observed evaporative heat loss from the skin... 

Humans are sensitive to moisture and can reliably describe the humidity of the environment using word scales as demonstrated in Fig. 5.12. The subject s humidity judgments appear to be functions of the air s dew point, a measure of absolute humidity, and are relatively unaffected by the ambient temperature. Further, people are also good at perceiving skin moisture, as illustrated in Fig. 5.13, where perceived skin wettedness is seen to correlate well with measured skin wettedness. 

Clothing can be one of the detractors from acceptability in humid envi-tonments. Measurements by Gwosdow- reveal that the friction between skin and clothing increases abruptly for skin wettedness levels above 25%. Further, fabrics are perceived to be roughet or to have a coarser texture and to be less pleasant with increasing skin moisture. This may be one of the reasons that, in the comfort studies cited earlier, the people have rarely indicated they were comfortable when they had skin wettedness levels near and above 25%. 

FIGURE S.I3 Perceived skin moisture correlated to measure skin wettedness for activities from I to 3 met. 

Comfort is reduced by elevated humidity levels. It is recommended that on the warm side of the comfort zone the relative humidity should not exceed 60% to prevent warm discomfort. On the cool side of the comfort zone, high humidity is less important because there is no swearing to increase skin moisture. For these reasons the upper boundaries of comfort zones in Fig. 5.7b are wet bulb temperatures of 18 and 20 °C for the winter and summer comfort zones respectively. 

The saponification process results in about 75 percent soap and 25 percent glycerin. In homemade soaps, the glycerin is left in, as it acts as an emollient (skin softener) and creates a nice feel. In commercial soaps, the glycerin is often removed and sold separately, sometimes showing up in skin moisturizers that remedy soap s skin-drying effects. 

Non-medicated moisturizers. Maintaining adequate skin moisture helps to control the scaling associated with psoriasis. Emollients restore skin pliability, reduce skin shedding, reduce pruritus, and help prevent painful cracking and bleeding.2 Non-medicated moisturizers may be liberally applied several times daily to help prevent skin dryness. Fragrance-free products should be selected when available. 

In addition, the use of biological monitoring has the advantage that skin penetration under particular conditions of protective clothing is included as well in the approach. The results of a dose-excretion study of propoxur by Meuling et al. (1991) using volunteers indicate a significant increase of the dermal uptake of the compound under conditions of occlusion, where there is increased blood flow, skin temperature, and skin moisture. 

Relation between external exposure, skin moisture, and internal dose... 

No significant relationship between the IPP excreted and hand exposure was observed for the applicators wearing normal work clothing or for protective clothing (p = 0.09 and p = 0.73, respectively). Skin moisture variables did not contribute significantly to the explained variation. 

The differences between the two trials were also studied for the IPP excretion and propoxur contamination of the hands and skin moisture as independent variables. For applicators, this resulted in a significant contribution of hand contamination to the model (p = 0.03, R2 = 0.4). Addition of skin moisture variables resulted in considerable increase of the R2 (up to 0.8), although without a significant contribution of the independent variables (Table 6). 

Meuling, W.J.A., Franssen, A. Ch., Brouwer, D.H., and van Hemmen, J.J. (1997) The influence of skin moisture on the deraml absorption of propoxur in human volunteers a consideration for biological monitoring practices, Sc. Total Environ., 199 165-172. 

Rieger, M.M. and Deems, D.E. (1974). Skin Moisturizers. II. The effects of cosmetic ingredients on human stratum comeum. J. Soc. Cosmet. Chem. 25 253. 

Skin moisturizing products should be carefully assessed for compatibility with any topical antimicrobial products being used and for physiological effects on the skin. 

Remove the polymer sample pan and lid carefully from the balance using forceps. (Note Skin moisture and oils will be left on the sample pan and lid if they are picked up by fingers. This extra mass will effect the DSC experiment.)... 

Add UV-absorbing compounds to a skin moisturizer and you have sunblock lotion. Making a sunblock lotion water resistant, however, is problematic. Upon exposure to water, the surfactants within the lotion help to remove the lotion. Manufacturers generally recommend that you reapply the lotion after swimming. Lotions that minimize the use of surfactants have increased water resistance, but they tend to be oily or greasy. For these reasons, many water-resistant formulas include compounds that polymerize into a nonpolar, water-resistant film that helps to hold the sunscreen agent on the skin when wet. 

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