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Purpose The main aims of this study were to describe the effects of incontinence pad composition on skin wetness, the skin/pad microclimate, and skin barrier function. We also evaluated the potential utility of our methods for future clinical investigation of absorbent pad design. Design Single-blind, quasi-experimental, open cohort design. Subjects and setting Twenty healthy older volunteers (mean age = 72.8 years, SD = 5.8 years; 8 male and 12 female) tested 2 absorbent pad types, with acquisition layers of different compositions (A and B) applied to different sites on the volar aspect of the forearms. One type A pad served as control (A dry) versus 3 pad samples wetted with 3 volumes of saline (A 15 mL, A 35 mL, and B 15 mL). The study was conducted within the clinical laboratory of a university nursing research group in the United Kingdom. Methods Skin barrier function was assessed by measuring transepidermal water loss (TEWL), stratum corneum (SC) hydration by corneometry, and skin surface pH using a standard skin pH electrode. Skin water loading (excess water penetration into the skin) was quantified by measuring TEWL and creating a desorption curve of the water vapor flux density. Calculating the area under the curve of the desorption curve to give skin surface water loss reflected excess water penetration into the skin. In a subgroup of the sample, the temperature and relative humidity (microclimate) at the interface between the skin and test pads were measured using a wafer-thin sensor placed between the skin and pad sample. Proinflammatory cytokine release from the SC was assessed using a noninvasive lipophilic film. The main outcome measures in this study were the differences in biophysical measurements of skin barrier function (TEWL, corneometer, and pH) before and after the application of the different pads. Results Mean ± SD baseline TEWL across all test sites was 10.4 ± 4.4 g/h/m. This increased to 10.6 ± 3.8 g/h/m at the control site, 15.3 ± 6.3 g/h/m for the A 15-mL pad, 15.3 ± 3.9 g/h/m for the A 35-mL pad, and 15.6 ± 3.2 g/h/m for the B 15-mL pad. The mean baseline skin surface pH was 5.9 ± 0.04; cutaneous pH increased to a mean of 6.1 ± 0.06 following all pad applications (P = .16). Mean SC hydration remained unchanged at the control site (A dry). In contrast, SC hydration increased following the application of all wetted pads. Target cytokines were detected in all samples we analyzed. The IL-1RA/IL-1α ratio increased following pad application, except for the wettest pad. Conclusion Study findings suggest that absorbent pad design and composition, particularly the acquisition layer, affect performance and may influence skin health. Based on our experience with this study, we believe the methods we used provide a simple and objective means to evaluate product performance that could be used to guide the future development of products and applied to clinical settings.

New findings What is the central question of this study? Ageing impairs the skin's thermal and tactile sensitivity: does ageing also induce loss of skin wetness sensitivity? What is the main finding and its importance? Older adults show an average 15% loss of skin wetness sensitivity, with this sensory deficit being mediated by a combination of reductions in skin's tactile sensing and hydration status. These findings increase knowledge of wetness sensing mechanisms across the lifespan. Abstract Humans use sensory integration mechanisms to sense skin wetness based on thermal and mechanical cues. Ageing impairs the skin's thermal and tactile sensitivity, yet we lack evidence on whether wetness sensing also changes with ageing. We mapped local skin wetness and temperature sensitivity in response to cold-, neutral- and warm-wet stimuli applied to the forehead, neck, lower back, dorsal foot, index finger and thumb, in 10 Younger (22.4 ± 1.1 years) and 10 Older (58.2 ± 5.1 years) males. We measured local skin temperature and conductance (i.e., a marker of hydration status) at the tested sites, to establish the role of skin's thermal and mechanical parameters in ageing-induced changes in wetness sensing. Irrespective of body site, Older reported overall lower wetness perceptions than Younger across all wet-stimulus temperatures (mean difference: -14.6 mm; 95% CI: -4.3, -24.9; P = 0.008; ∼15% difference). When considering regional wetness sensitivity, the effect of ageing was more pronounced in response to the cold-wet stimulus over the lover back (mean difference Older vs. Younger: -36.8 mm; 95% CI: -68.4, -5.2; P = 0.014; ∼37% difference) and dorsal foot (mean difference: -37.1 mm; 95% CI: -68.7, -5.5; P = 0.013; ∼37% difference). We found no differences between age groups on overall thermal sensations (P = 0.744) nor local skin temperature (P = 0.372); however, we found that Older presented overall lower skin conductance than Younger (mean difference: -1.56 μS; 95% CI: -0.49, -2.62; P = 0.005), which corresponded to an ∼78% reduction in skin hydration. We conclude that skin wetness sensing decreases with ageing primarily due to age-induced changes in skin mechanics and tactile sensitivity.

KEY POINTS Skin wetness occurring secondary to the build-up of sweat on the skin provokes thermal discomfort, the precursor to engaging in cool-seeking behaviour. Associative evidence indicates that skin wetness stimulates cool-seeking behaviour to a greater extent than increases in core and mean skin temperatures. The independent contribution of skin wetness to cool-seeking behaviour during heat stress has never been established. We demonstrate that skin wetness augments cool-seeking behaviour during passive heat stress independently of differential increases in skin temperature and core temperature. We also identify that perceptions of skin wetness were not elevated despite increases in actual skin wetness. These data support the proposition that afferent signalling from skin wetness enhances the desire to engage in cool-seeking behaviour during passive heat stress. ABSTRACT This study tested the hypothesis that elevations in skin wetness augments cool-seeking behaviour during passive heat stress. Twelve subjects (6 females, age: 24 ± 2 y) donned a water-perfused suit circulating 34 °C water and completed two trials resting supine in a 28.5 ± 0.4 °C environment. The trials involved a 20 min baseline period (26 ± 3% relative humidity (RH)), 60 min while ambient humidity was maintained at 26±3% RH (LOW) or increased to 67 ± 5% RH (HIGH), followed by 60 min passive heat stress (HS) where the water temperature in the suit was incrementally increased to 50 °C. Subjects were able to seek cooling when their neck was thermally uncomfortable by pressing a button. Each button press initiated 30 s of -20 °C fluid perfusing through a custom-made device secured against the skin on the dorsal neck. Mean skin (Tskin ) and core (Tcore ) temperatures, mean skin wetness (Wskin ) and neck device temperature (Tdevice ) were measured continuously. Cool-seeking behaviour was determined from total time receiving cooling (TTcool ) and cumulative button presses. Tskin and Tcore increased during HS (P

Purpose. To investigate the effect of cold stimulation (contacting wet fabric) and tactile stimulation (dynamic friction) on skin wetness perception: (a) wetness perception of fabric with different...

Contemporary approaches to pressure injury (PI) risk identification rely on the use of risk assessment tools and visual skin assessment. Objective biophysical measures that assess skin hydration, melanin, erythema and lipids have not been traditionally used in PI risk; however, these may prove useful as a risk assessment tool. The relationship between subjective visual assessments of skin condition, biophysical measures and PI risk warrants investigation. This study used a descriptive correlational design to examine the relationship between measures of skin hydration, colour (melanin and erythema) and lipids at PI-prone areas amongst geriatric persons (n = 38), obtained using biophysical skin measures and visual skin assessment. Twice daily measures of epidermal hydration, colour and lipids were assessed using the SD202 Skin Diagnostic (Courage + Khazaka GmBH, Cologne, Germany) over pressure-prone areas of the body of study participants over seven consecutive days. Concurrent visual assessment of skin hydration and colour was performed. Results obtained using the SD202 Skin Diagnostic were compared with results gathered from visual assessment and examined for their association with participants' PI risk based on scores of the Norton Risk Assessment Scale. While epidermal hydration and skin colour reading scores did not vary significantly over the data collection period, lipid readings could not be registered on any occasion. With the exception of skin dryness, skin parameters via both objective and subjective means had significant, positive correlations. Statistically significant correlations emerged between visual assessment of skin wetness at the sacrum (r = -0·441, P < 0·01) and ischia (r = -0·468, P < 0·01) and Norton Risk Assessment Scale scores. It was found that the objective assessment of epidermal hydration (skin wetness) was also significantly associated with PI risk at the sacrum (r = -0·528, P < 0·01), as well as the right ischia (r = -0·410, P < 0·05) and left ischia (r = -0·407, P < 0·05). Erythema, when assessed objectively, was significantly correlated with PI risk at the sacrum (r = -0·322, P < 0·05). Such findings indicating that the finer measures afforded by the SD202 Skin Diagnostic in the assessment of the subtle red hues displayed in erythematous skin may provide an additional advantage over traditional, clinician assessment.

The ability to perceive thermal changes in the surrounding environment is critical for survival. However, sensing temperature is not the only factor among the cutaneous sensations to contribute to thermoregulatory responses in humans. Sensing skin wetness (i.e. hygrosensation) is also critical both for behavioral and autonomic adaptations. Although much has been done to define the biophysical role of skin wetness in contributing to thermal homeostasis, little is known on the neurophysiological mechanisms underpinning the ability to sense skin wetness. Humans are not provided with skin humidity receptors (i.e., hygroreceptors) and psychophysical studies have identified potential sensory cues (i.e. thermal and mechanosensory) which could contribute to sensing wetness. Recently, a neurophysiological model of human wetness sensitivity has been developed. In helping clarifying the peripheral and central neural mechanisms involved in sensing skin wetness, this model has provided evidence for the existence of a specific human hygrosensation strategy, which is underpinned by perceptual learning via sensory experience. Remarkably, this strategy seems to be shared by other hygroreceptor-lacking animals. However, questions remain on whether these sensory mechanisms are underpinned by specific neuromolecular pathways in humans. Although the first study on human wetness perception dates back to more than 100 years, it is surprising that the neurophysiological bases of such an important sensory feature have only recently started to be unveiled. Hence, to provide an overview of the current knowledge on human hygrosensation, along with potential directions for future research, this review will examine the psychophysical and neurophysiological bases of human skin wetness perception.

Background/purpose: In the absence of humidity receptors in human skin, the perception of skin wetness is considered a somatosensory experience resulting from the integration of temperature (particularly cold) and mechanical inputs. However, limited data are available on the role of the temperature sense. Methods: Wet and dry stimuli at 4 and 8°C above local skin temperature were applied on the back of 7 participants (age 21± 2 years) while skin temperature and conductance, thermal and wetness perceptions were recorded. Results: Resting local skin temperature always increased by the application of the stimuli (+0.5 to +1.4°C). No effect of stimulus wetness was found on wetness perceptions (p>0.05). The threshold (point “-2 slightly wet” on the wetness scale) to identify a clearly perceived wetness was never reached during any stimulations and participants did not perceive that some of the stimuli were wet. Overall, warm temperature stimuli suppressed the perception of skin wetness. Conclusions: We conclude that it is not the contact of the skin with moisture per se, but rather the integration of particular sensory inputs (amongst which coldness seems dominant) which drives the perception of skin wetness during the initial contact with a wet surface.

Cold sensations are suggested as the primary inducer of the perception of skin wetness. However, limited data are available on the effects of skin cooling. Hence, we investigated the role of peripheral cold afferents in the perception of wetness. Six cold-dry stimuli (producing skin cooling rates in a range of 0.02 to 0.41°C/s) were applied on the forearm of 9 female participants. Skin temperature and conductance, thermal and wetness perception were recorded. Five out of 9 participants perceived wetness as a result of cold-dry stimuli with cooling rates in a range of 0.14 to 0.41°C/s, while 4 did not perceive skin wetness at all. Although skin cooling and cold sensations play a role in evoking the perception of wetness, these are not always of a primary importance and other sensory modalities (i.e. touch and vision), as well as the inter-individual variability in thermal sensitivity, might be equally determinant in characterising this perception.

Background/purpose: Excessive skin hydration from occlusive coverings such as absorbent articles, bandages, etc. has been known to compromise the skin's barrier properties. Damage to the stratum corneum occurs from prolonged exposure to wetness and limited product breathability, which reduces evaporation. Protection from wetness may be imparted by barrier materials, such as lotions and ointments on the skin. Barrier materials are traditionally applied by hand from bulk containers (bottle or tube). In recent years, diapers have been made that contain barrier ointments designed to transfer to the skin during wear. The purpose of this research was to develop a reliable in vivo method for evaluating skin wetness protection when using personal products. Method: The means for evaluating wetness protection in vivo is dye exclusion evaluation on human skin. Dye exclusion involves application of a barrier material, followed by dye application and skin staining evaluation. The dye exclusion method may be conducted on adult forearms with direct application of the barrier material or on infant or adult torsos after wearing a diaper or incontinence product (or other personal products) that contains the barrier material. Dye exclusion on infants used cosmetic dyes (safe for use in the eye area). Results: Dye exclusion demonstrated skin protection on both adult forearms and on infant buttocks. Ointments in diapers protected the skin from the dye when diapers were worn from a few hours to several days (with appropriate changes of product). Conclusion: The dye exclusion method was able to demonstrate the advantage of barrier ointments for wetness protection and also to discriminate between ointment formulations.

Although the ability to sense skin wetness and humidity is critical for behavioural and autonomic adaptations, humans are not provided with specific skin receptors for sensing wetness [1]. We have recently demonstrated that humans perceive the wetness experienced when the skin is in contact with a wet surface through a multisensory integration of thermal and tactile inputs generated by the interaction between skin and moisture [2]. To further the understanding on the neurophysiology of human skin wetness perception, here we tested the hypothesis that the perception of sweat-induced skin wetness can be significantly manipulated, independently from the level of physical skin wetness.

Humans sense the wetness of a wet surface through the somatosensory integration of thermal and tactile inputs generated by the interaction between skin and moisture. However, little is known on how wetness is sensed when moisture is produced via sweating. We tested the hypothesis that, in the absence of skin cooling, intermittent tactile cues, as coded by low-threshold skin mechanoreceptors, modulate the perception of sweat-induced skin wetness, independently of the level of physical wetness. Ten males (22 yr old) performed an incremental exercise protocol during two trials designed to induce the same physical skin wetness but to induce lower (TIGHT-FIT) and higher (LOOSE-FIT) wetness perception. In the TIGHT-FIT, a tight-fitting clothing ensemble limited intermittent skin-sweat-clothing tactile interactions. In the LOOSE-FIT, a loose-fitting ensemble allowed free skin-sweat-clothing interactions. Heart rate, core and skin temperature, galvanic skin conductance (GSC), and physical ( wbody) and perceived skin wetness were recorded. Exercise-induced sweat production and physical wetness increased significantly [GSC: 3.1 μS, SD 0.3 to 18.8 μS, SD 1.3, P < 0.01; wbody: 0.26 no-dimension units (nd), SD 0.02, to 0.92 nd, SD 0.01, P < 0.01], with no differences between TIGHT-FIT and LOOSE-FIT ( P > 0.05). However, the limited intermittent tactile inputs generated by the TIGHT-FIT ensemble reduced significantly whole-body and regional wetness perception ( P < 0.01). This reduction was more pronounced when between 40 and 80% of the body was covered in sweat. We conclude that the central integration of intermittent mechanical interactions between skin, sweat, and clothing, as coded by low-threshold skin mechanoreceptors, significantly contributes to the ability to sense sweat-induced skin wetness.

The ability to sense humidity and wetness is an important sensory attribute for many species across the animal kingdom, including humans. Although this sensory ability plays an important role in many human physiological and behavioural functions, as humans’ largest sensory organ i.e. the skin seems not to be provided with specific receptors for the sensation of wetness (i.e. hygroreceptors), the neurophysiological mechanisms underlying this complex sensory experience are still poorly understood. The aim of this Thesis was to investigate the neurophysiological mechanisms underpinning humans’ remarkable ability to sense skin wetness despite the lack of specific skin hygroreceptors. It was hypothesised that humans could “learn” to perceive the wetness experienced when the skin is in contact with a wet surface or when sweat is produced through a complex multisensory integration of thermal (i.e. heat transfer) and tactile (i.e. mechanical pressure and friction) inputs generated by the interaction between skin, moisture and (if donned) clothing. Hence, as both thermal and tactile skin afferents could contribute significantly to drive the perception of skin wetness, their role in the peripheral and central sensory integration of skin wetness perception was investigated, both under conditions of skin’s contact with an external (dry or wet) stimulus as well as during the active production of sweat.

Objective Pressure ulcers often occur at sites subjected to pressure and wetness. Although skin wetness is a risk factor for pressure ulcers,the mechanisms and effects of wetness versus urine constituents on skin breakdown is unclear. The hypothesis that wetness reduces skin hardness and, thereby, increases vulnerability of underlying blood vessels to pressure-induced flow reductions was tested in this study. Design Pads saturated with water and with a water solution mixed with the main chemical constituents of urine (synthetic urine; s-urine) were applied to forearm skin of 10 healthy subjects for 5.5 hours. Skin hardness, blood flow change caused by 60 mm Hg of pressure, erythema, and temperature were compared among dry, water, and s-urine test sites. Participants 10 healthy women. Setting Research Center, Nova Southeastern University, Health Professions Division, Fort Lauderdale, FL. Main results S-urine and water caused significant reductions in initial hardness and caused greater initial perfusion decreases during pressure load when compared with dry sites. Skin temperature and erythema were lower at wet sites when compared with dry sites. Conclusions The findings of this study are consistent with the concept that sustained skin wetness increases vulnerability to pressure-induced blood flow reduction. The effect appears to be mainly dependent on wetness, but urine constituents may exacerbate the effect. In addition, wetness-related skin cooling may play a role. In the healthy subjects studied, the blood flow decrease was not sustained due to perfusion recovery under pressure. Skin wetness would likely have more sustained effects in patients with compromised recovery mechanisms. Measures to diminish skin exposure to wetness in these patients, whatever the wetness source, are an important consideration in a multifaceted strategy to reduce the risk of pressure ulcers.

Background/aims: Excessive skin hydration resulting from wet undergarments is a major cause of diaper rash in children and contributes to severe dermatitis in incontinent adults. Advancements in absorbent technology have led to diapers and incontinent garments that not only absorb urine, but also transfer it to different regions, and lock it away from the skin. The purpose of the present study was to develop a reliable method to assess the effectiveness of absorbent articles in mitigating skin hydration. Methods: Disposable diapers with different absorbent structures were wrapped around the forearms of adult volunteers, loaded with urine substitute, and held in place for 1 h. Hydration of the volar region was measured by evaporimetry and compared with that of skin in the diaper region of children who had worn control loaded diapers in the usual way. The amount of fluid retained in various diaper layers and in the superabsorbent polymer core was measured. Conclusions: Evaporative water loss measurement on adult forearms was shown to be a reliable test for comparing the effectiveness of absorbent articles in preventing excessive skin hydration provided that 1) the complete garment was used and 2) fluid was loaded in a manner that simulated normal urination. Skin on adult forearms and skin in the diaper region of children were concordant in their response to wet diapers. Skin wetness was directly related to the amount of liquid retained in absorbent layers close to the skin.

Humidity receptors have never been identified on human skin and the ability to perceive skin wetness has been suggested to rely on the sensory inputs arising from thermal cold afferents. However, limited data are available on how thermal afferents and their regional distribution influence the perception of wetness. PURPOSE: Given the regional variability in thermal sensitivity across the torso, here we examined whether regional differences in the sensitivity to wetness exist.

Skin wetness is proportional to diaper wetness, and with increased skin wetness, the potential for diaper dermatitis is increased. This study evaluated a wide range of infant diaper products. Eighty healthy volunteers wore 2-inch wetted diaper patches on their volar forearm for two hours. An evaporimeter was used to measure excess skin wetness attributed to the patches. The amount of moisture retained in the patch was also calculated. We found that superabsorbent (SA) disposable diapers kept the skin drier and retained more synthetic urine than cloth reusable and conventional disposable brands, and thus have the greatest potential for helping prevent diaper dermatitis. The SA brands evaluated did an equally adequate job in keeping the skin dry and in retaining moisture. Conventional disposable diapers were less able to keep the skin dry than SA diapers and were not superior to cloth products in most instances. Cloth diapers” performance depended on their composition. Those with several layers of the same fabric were less successful in keeping the skin dry than ones that contained middle layers of different nonwoven components.

The strength of the association between diaper dermatitis and measurements of skin wetness and skin pH was evaluated by statistical analysis of four diaper trials involving 1601 infants. Although the strength of the association between skin wetness and diaper dermatitis was greater than that between skin pH and diaper dermatitis, increases in wetness and pH were both significantly associated with elevated mean grades for diaper dermatitis. The skin environment least likely to be associated with diaper dermatitis is one In which Increases In both skin wetness and skin pH are minimized.

Wearing dry and wet cloth and disposable diaper materials has certain effects on the degree of skin wetness. These, in turn, affect the coefficient of skin friction, the skin's susceptibility to abrasion damage, its permeability, and its support of microbial growth. These effects were explored using an adult model wearing forearm patches. The adult model was validated by comparisons of skin wetness and friction values for infants and adults determined under similar conditions. Skin wetness was proportional to diaper wetness. With increased skin wetness, there were increased coefficients of friction and increased abrasion damage, skin permeability, and microbial growth. Cloth diaper material produced wetter skin than did disposable diaper material at equivalent loadings.

Diaper dermatitis results from the action of a number of physical and chemical factors on the skin. While its etiology is complex, there is agreement that prolonged contact between wet diapers and the skin leading to excessive hydration of the stratum corneum and reduced barrier function is a primary factor. Recent research also indicates that pH elevation resulting from ammonia production increases the probability of skin damage due to fecal enzyme activity. New diapers containing absorbent polymers blended with cellulose fluff in the absorbent core have been developed. The absorbent polymer binds fluids and controls pH in the diaper environment. To assess the effectiveness of these diapers, a clinical study was conducted with approximately 150 infants over 15 weeks, using fluff diapers and absorbent polymer diapers. The results clearly showed that the diapers with absorbent polymer provide a better skin environment than those with fluff only with respect to lower skin wetness and pH control (instrumental measurements). In addition, the clinicians' grades indicated a directional reduction in diaper rash severity.