[Systemic emulsions. 2. Use of different methods of formulation: the effect of essential oils of thyme on stability]. / Etude des systèmes émulsionnés. II. Application des différentes méthodes de formulation: introduction d'huile essentielle de thym, incidence sur la stabilité.

As part of an ongoing investigation on emulsifying techniques, we studied the influence of different essential oils from Thymus vulgaris on emulsion stability. All four chimiotypes tested (geraniol, linalol, carvacrol, and thymol) caused a marked decrease in stability. This instability cannot be explained by a change in the hydrophilic lipophilic balance since the HLBc of the new oil phase (essential oil + paraffine oil) was not significantly different from that of paraffine alone.

TEWL measurement standardization: kinetic and topographic aspects.

The aim of this study was to standardize the recording technique of the SERVO MED Ep 1C to determine the rest time required for human subjects to obtain stabilized values of transepidermal water loss (TEWL). Measurements of TEWL were performed on the flexor side of the forearm in healthy volunteers. First, different sites were tested on different days to study intra- and inter-individual variations. The recordings were carried out every 5 min for 2 h. Values reached a linear state after 15 min of rest. A time-course type curve of TEWL was established.

Evaluation expérimentale de l'hydratation et du pouvoir occlusif in vivo et in vitro d'excipients lipophiles et de leurs émulsions phase huile continue.

Synopsis A study was carried out on three water in oil emulsions and their respective oil-phases, petrolatum, liquid paraffin and sweet almond oil, in order to compare their occlusive properties and thus their influence on cutaneous hydration. An in vitro method using 'Patel'cells in a water-saturated atmosphere at controlled temperature enabled, in the first instance, the various emulsions and their oil-phases to be classified according to their permeability to water vapour. The results are in order of increasing degree of occlusion: sweet almond oil, liquid paraffin and petrolatum. In in vivo studies on human volunteers, the influence of the application of the same substances on transepidermal water loss (TEWL) and cutaneous hydration was measured with an evaporimeter and a corneometer, in a temperature and humidity-controlled room. Measurements were performed on the flexor side of the forearm after sodium lauryl sulphate 5% insult on six subjects at times of 0, 30, 120 and 270 min. The different oils, used pure, increased the hydration by an occlusive effect, and this was described by measurements of TEWL. On the other hand, after using the emulsions, the increase in hydration noted does not appear to involve an occlusive mechanism.

[Emulsion systems. I. Comparison of different formulation methods]. / Etude des systèmes émulsionnés. I. Comparaison des différentes méthodes de formulation.

This paper examines different technics of emulsifying systems formulation: those using the research of HLBc and those using the phase diagram. The comparison of these two methods of formulation permits us to describe one method looking for the HLBc of each proportions of the phase diagram. So a volume is determined allowing to choose more securely the surfactants proportions and also to end on surer formulation.