Skin Health Connected to the Use of Absorbent Hygiene Products: A Review.

Over the past 50 years, absorbent hygiene products such as baby diapers and incontinence products have become essential features of modern day life. Through innovation and enhanced technology, their design, composition and performance have been dramatically upgraded from their early forms, and they have transformed the lives of millions of people, improving their quality of life. Skin health related to the use of absorbent hygiene products has accordingly also greatly improved. Still, the wearing of absorbent hygiene products will affect the skin, and for some users the changes in microclimate, mechanical interactions and the exposure to urine and faeces may result in irritant contact dermatitis, i.e. diaper dermatitis (DD) or incontinence-associated dermatitis (IAD). Babies with developing skin and the elderly with deteriorating skin functions who are the most frequent users of absorbent hygiene products are more vulnerable to the causal factors. Although irritant reactions are the most common, allergic contact dermatitis should be considered if a DD/IAD fails to improve by recommended actions. There is also a connection between IAD and pressure ulcer development of which it is important to be aware. A holistic approach of using high-quality absorbent hygiene products in combination with appropriate skin care will help maintaining good skin health.

Meritocratic sharing is based on collaboration in 3-year-olds.

The present study investigated young preschoolers' proportional allocation of rewards in 2 different work contexts. We presented 32 pairs of 3.5-year-old peers with a collaborative task to obtain rewards by pulling ropes. In order to establish differences in work input, 1 child's rope was not immediately accessible but had to be retrieved from the apparatus by means of a specific tool, while the other child had no such additional work to do. The result of the game was that 1 individual received 1 toy and the other received 3 toys. In the Deserving condition, the working child received the 3 toys (thus work and reward matched), whereas in the Undeserving condition, the other child received the 3 toys (he or she was overpaid, and the working child was underpaid). Another 32 dyads participated in a noncollaborative, parallel work task, again in a Deserving condition and an Undeserving condition. On average, children with 3 toys shared with their partner more in the Undeserving condition than in the Deserving condition after collaboration but not in a parallel work setup. These results suggest that young children take merit into account in distributing resources at a much younger age than previously believed and that peer collaboration is an especially facilitative context for children's attention to norms of fairness.

Lipid cubic phases in topical drug delivery: visualization of skin distribution using two-photon microscopy.

The distribution of sulphorhodamine B (SRB), a fluorescent hydrophilic model drug, was investigated in human skin after passive diffusion using four different topical delivery systems. The delivery vehicles applied were two bicontinuous lipid cubic systems, a commercial ointment and water. The lipid cubic systems consisted of either monoolein (MO) or phytantriol (PT) and water. The formulations were applied on full-thickness human skin during 24 h. Thereafter the samples were investigated using two-photon microscopy (TPM). The TPM system consisted of an inverted microscope with a 40x water-immersion objective, laser scan-box, and a pulsed femtosecond titanium:sapphire laser operating at 780 nm. The fluorescence was detected using a 560 nm long-pass filter. Sequential optical sectioning was performed, resulting in images obtained at different tissue depths. TPM revealed that SRB mainly penetrates the skin via the intercellular lipid matrix. Samples exposed to the cubic phases showed a higher accumulation of SRB in micro-fissures, from which a fluorescent network of threadlike structures spread laterally in the tissue. These structures were also detected in some of the ointment samples, but not as frequent. The penetration of SRB into the stratum granulosum was deduced from the fluorescence of SRB present inside polygonal keratinocytes with cell nuclei. Higher SRB fluorescence was obtained in the outermost layer of the epidermis using the bicontinuous cubic phases, compared to when using the reference formulations. Thus, our results suggest that the dominating delivery route using the cubic phases is via micro-fissures caused by microscopic clustering of the keratinocytes in the skin. From these micro-fissures hydrophilic compounds, here modeled by SRB, can diffuse into the surrounding intercellular lipid matrix acting like a source for sustained release.

Structure and dynamics of a sponge phase in the methyl delta-aminolevulinate/monoolein/water/propylene glycol system.

The structural effect caused by the addition of up to 16% (w/w) of the hydrochloride salt of delta-aminolevulinic acid (ALA, HOOC-CH2-CH2-CO-CH2-NH2HCl) or its methyl ester (m-ALA) to the sponge phase formed of monoolein/water/propylene glycol was investigated by means of crossed polarizers, small angle X-ray diffraction (SAXD) and nuclear magnetic resonance diffusometry (NMRD). Inspection with crossed polarizers revealed that additions of 4-16% (w/w) m-ALA transformed the isotropic bicontinuous sponge phase partly (4-10%) or completely (13 and 16%) into an anisotropic lamellar phase, indicating that m-ALA has a flattening effect on the bilayer curvature. The addition of 16% (w/w) ALA did not show any effect on the sponge phase. By addition of water to the anisotropic m-ALA samples, isotropic liquids were re-formed. The SAXD data for the isotropic liquids showed a diffuse Bragg peak and the NMRD self-diffusion coefficients for the drug (m-ALA) and the components of the original sponge phase (monoolein, water and propylene glycol) were shown to be essentially constant for 0-16% (w/w) added m-ALA. These results confirmed the hypothesis that the re-formed isotropic phases were indeed sponge phases. Water, for example, showed a diffusion coefficient of 3.1-3.9x10(-10)m(2)s(-1) in the sponge phase, compared to 5.3-5.7 x 10(-10)m2s(-1) in relevant water/propylene glycol solutions or 2.3 x 10(-9)m2s(-1) in pure water. The reduction can be explained as a consequence of the microstructure (congruent monoolein bilayer) of the sponge phase and of the viscosity effect caused by propylene glycol and m-ALA.

Aqueous self-assembly of phytantriol in ternary systems: effect of monoolein, distearoylphosphatidylglycerol and three water-miscible solvents.

The aqueous phase behavior of phytantriol (PT) in mixtures of monoolein (MO), distearoylphosphatidylglycerol (DSPG), propylene glycol (PG), polyethylene glycol 400 (PEG 400) and 2-methyl-2,4-pentanediol (MPD) was investigated by visual inspection, polarized light microscopy and small angle X-ray diffraction at room temperature. The phase diagrams of PT and MO in water are qualitatively very similar and PT/MO mixtures in excess water form one cubic phase of space group Pn3m irrespective of mixing ratio. The addition of the charged membrane lipid DSPG to the PT system gives rise to a considerable water swelling of the cubic phases as well as the occurrence of a cubic phase of space group Im3m. Whereas all three solvents studied give rise to a sponge (L3) phase in the MO-water system, this phase was only found when MPD was added to the PT-water system. The results are discussed with respect to the chemical differences between PT and MO.

Lipid cubic phases for improved topical drug delivery in photodynamic therapy.

We have evaluated the efficacy of lipid cubic phases, highly ordered self-assembly systems on the nanometer level, as drug delivery vehicles for in vivo topical administration of delta-aminolevulinic acid (ALA) and its methyl ester (m-ALA) on nude mice skin. ALA, a precursor of heme, induces the production of the photosensitizer protoporphyrin IX (PpIX) in living tissue. Measuring the PpIX fluorescence at the skin surface, after topical administration, makes indirect quantification of the penetration of ALA into the tissue possible. Cubic phases were formed of lipid (monoolein or phytantriol), water and drug. In some cases, propylene glycol was included in the cubic phase as well. The drug concentration was 3% (w/w, based on the total sample weight) in all investigated vehicles. When the formulations were applied for 1 h, the monoolein cubic systems and the three-component phytantriol sample showed higher fluorescence compared to the standard ointment during the 10 h of measurement. Both ALA and m-ALA yielded similar results, although the differences between the investigated vehicles were more pronounced when using m-ALA. For the 24-h applications, the monoolein cubic systems with m-ALA showed faster PpIX formation than the standard ointment, implying higher PpIX levels at short application times (less than 4 h). The systemic PpIX fluorescence of ALA was elevated by using the lipid cubic formulations. Notably, a small systemic effect was also observed for the monoolein cubic sample with m-ALA. These results imply improved PpIX formation when using the lipid cubic systems, most probably due to enhanced drug penetration.