High resolution skin colorimetry, strain mapping and mechanobiology.

in International Journal of Cosmetic Science (2010), 32(4), 241-5

SYNOPSIS: Skin colours are notoriously different between individuals. They are governed by ethnicities and phototypes, and further influenced by a variety of factors including photoexposures and sustained ... [more ▼]

SYNOPSIS: Skin colours are notoriously different between individuals. They are governed by ethnicities and phototypes, and further influenced by a variety of factors including photoexposures and sustained mechanical stress. Indeed, mechanobiology is a feature affecting the epidermal melanization. High-resolution epiluminescence colorimetry helps in deciphering the effects of forces generated by Langer's lines or relaxed skin tension lines on the melanocyte activity. The same procedure shows a prominent laddering pattern of melanization in striae distensae contrasting with the regular honeycomb pattern in the surrounding skin. [less ▲]

Kinetics of moisturizing and firming effects of cosmetic formulations.

in International Journal of Cosmetic Science (2008), 30(2), 131-8

The assessment of cosmetic efficacy is rarely performed in studies comparing different concentrations of active compounds. The aim of the present study was to determine the skin hydrating and the skin ... [more ▼]

The assessment of cosmetic efficacy is rarely performed in studies comparing different concentrations of active compounds. The aim of the present study was to determine the skin hydrating and the skin firming dose-response effects of cosmetic formulations enriched in compounds derived from algae and fish collagen. A series of factors were studied including the type of formulation (cream or serum), the concentration in active ingredients, the effect of repetitive applications, as well as any residual effect of the formulations after stopping their applications. The serum enriched in marine compounds showed a better moisturizing effect in short term. The cream appeared more active later, particularly following repeat applications. A sustained tensor (firming) effect was observed during treatment with both the lotion and the cream. However, no remnant firming effect was perceived after stopping treatment. [less ▲]

Skin in maturity: the endocrine and neuroendocrine pathways.

in International Journal of Cosmetic Science (2007), 29(1), 1-6

Irrespective of age, most of the skin components are under the physiological control of endocrine and neuroendocrine factors. There is evidence that skin ageing appears complex showing much ... [more ▼]

Irrespective of age, most of the skin components are under the physiological control of endocrine and neuroendocrine factors. There is evidence that skin ageing appears complex showing much interindividual variability. Conceptually, ageing is a single biological process that is influenced and modulated by a series of various internal and exogenous factors. Among them, hormones and neuroendocrine signals play key roles in several ways. Ageing of most endocrine glands will in turn alter the skin biology. In addition, the age-related reduction in the intrinsic neuroendocrine activity of the skin will also alter the ageing rate of this organ. At last, various endocrinopathies will boost or conversely decrease the severity of the signs of cutaneous ageing. [less ▲]

Revisiting dandruff.

in International Journal of Cosmetic Science (2006), 28(5), 311-8

Dandruff is a common scalp disorder affecting almost half of the postpubertal population of any ethnicity and both genders. It may, however, represent a stubborn esthetical disturbance often source of ... [more ▼]

Dandruff is a common scalp disorder affecting almost half of the postpubertal population of any ethnicity and both genders. It may, however, represent a stubborn esthetical disturbance often source of pruritus. Skin biocenosis, in particular the Malassezia spp. flora, plays a key aetiologic role, in combination with the unusual capacity of some corneocytes to be coated by these yeasts. Substantial evidence indicates that keratinocytes play an active role in the generation and expression of immunopathological reactions. This is probably the case in dandruff. Upon stimulation of a critical colonization of corneocytes by Malassezia yeasts, the release of pro-inflammatory mediators is increased. This could lead to the subclinical microinflammation present in dandruff. In seborrheic dermatitis, local deposits of immunoglobulins and the release of lymphokines are responsible for the recruitment and local activation of leukocytes leading to the eventual amplification of the inflammatory reaction. Some ancillary non-microbial causes of dandruff may operate through physical or chemical irritants. Many methods have been described for rating dandruff. Our favourite tools are clinical examination and squamometry. Dandruff can precipitate telogen effluvium and exacerbate androgenic alopecia. Antidandruff formulations exhibiting some direct or indirect anti-inflammatory activity can improve both dandruff and its subsequent hair cycle disturbance. [less ▲]

Cellulite histopathology and related mechanobiology.

in International Journal of Cosmetic Science (2006), 28(3), 207-10

Cellulite, sometimes called gynoid lipodystrophy, is much more prevalent in women than in men. There are glaring discrepancies regarding the microanatomical descriptions of this condition in the ... [more ▼]

Cellulite, sometimes called gynoid lipodystrophy, is much more prevalent in women than in men. There are glaring discrepancies regarding the microanatomical descriptions of this condition in the literature. A lumpy aspect of the dermo-hypodermal interface is often cited, but it appears to represent a gender-linked characteristic of the thighs and buttocks without being a specific sign of cellulite. Incipient cellulite recognized by a discrete padded look or 'orange peel' aspect appears correlated with the presence of a network of focally enlarged fibrosclerotic strands partitioning the hypodermis and serving as a physiological buttress limiting the outpouching of fat lobules on pinching the skin. These connective tissue structures might represent a hormonal-dependent reactive process to sustained mechanical tensions caused by the adipocyte lobules. Full blown cellulite is recognized by a lumpy-bumpy and dimpled skin surface. It likely represents subjugation of the hypertrophic response of the hypodermal connective tissue strands when their resistance is overcome by progressive fat accumulation. In these cases, histological aspects reminiscent of striae distensae are identified within the hypodermal connective tissue strands. The mechanical properties of skin involved by cellulite process are altered, but may tend to resume to normal under treatment. These functional changes influence the mechanobiology of connective tissue cells, in particular the Factor XIIIa-positive dermal dendrocytes. [less ▲]

Irritation cutanee et vitesse de propagation d'ondes ultrasonores.

in International Journal of Cosmetic Science (2003), 25(1-2), 31-5

Cutaneous irritation is a stereotyped response of the skin to any physical or chemical insult. Its main manifestations encompass inflammatory erythema and an alteration of the cutaneous microrelief ... [more ▼]

Cutaneous irritation is a stereotyped response of the skin to any physical or chemical insult. Its main manifestations encompass inflammatory erythema and an alteration of the cutaneous microrelief showing increased roughness, dehydration and erratic desquamation. Several instrumental methods can indirectly assess the issues of cutaneous irritation on human stratum corneum. The aim of the present study was to measure the speed of propagation of ultrasound shear waves in the skin irritated by anionic surfactants. The study was performed in 25 healthy subjects of both sexes. Occlusive patches of a 10% solution of anionic surfactants were applied to a forearm of each volunteer. The other forearm served as an untreated control site. Patches remained in place for 24 h. Three hours later, another patch was placed again for 21 h. Resonance running time measurements (RRTM) of the ultrasound shear wave were performed using a Reviscometer((R)) RVM 600. Measurements were performed at entry in the study and 2 days after removing the second patch. Desquamative xerosis was obvious at the sites patched with the surfactant solution. RRTM values were significantly (P < 0.0001) lower than those at the control site. Hence, the speed of propagation of ultrasound shear waves was shown to be increased at an irritated site compared to an intact site. In conclusion, this study shows that the propagation speed of ultrasounds is influenced by the skin surface nature, being considerably increased in skin altered by surfactants. [less ▲]

Effect of residence time on the efficacy of antidandruff shampoos.

in International Journal of Cosmetic Science (2003), 25(6), 267-71

Dandruff is known to be controlled by fungistatic shampoos active against Malassezia spp. These products also remove the loosely attached scales. This study was performed to assess the effect of a 5-min ... [more ▼]

Dandruff is known to be controlled by fungistatic shampoos active against Malassezia spp. These products also remove the loosely attached scales. This study was performed to assess the effect of a 5-min residence time on the efficacy of antidandruff shampoos. Two commercially available shampoos were used in two groups of 21 panelists with severe dandruff. They contained either 1% ketoconazole or 1% piroctone olamine. In each group, intraindividual comparisons were made by a split-scalp design between the effect of a 5-min residence time versus no residence time. Both shampoos induced significant reductions in scaliness and yeast colonization. The beneficial effects were obvious immediately after one single shampooing and 3 days later as well. The improvement was greater with a 5-min residence time. The piroctone olamine treatment benefited more than the ketoconazole treatment from the extension of shampoo-exposure time. In conclusion, the benefit of a residence time in treating dandruff is documented. The level of improvement in efficacy may vary according to the nature of the shampoo. [less ▲]

Nudging hair shedding by antidandruff shampoos. A comparison of 1% ketoconazole, 1% piroctone olamine and 1% zinc pyrithione formulations.

in International Journal of Cosmetic Science (2002), 24(5), 249-56

Hair shedding and hair thinning have been reported to be affected by dandruff and seborrhoeic dermatitis. The present study was conducted in 150 men presenting with telogen effluvium related to androgenic ... [more ▼]

Hair shedding and hair thinning have been reported to be affected by dandruff and seborrhoeic dermatitis. The present study was conducted in 150 men presenting with telogen effluvium related to androgenic alopecia associated with dandruff. They were randomly allocated to three groups receiving each one of the three shampoos in the market containing either 1% ketoconazole (KTZ), 1% piroctone olamine (PTO) or 1% zinc pyrithione (ZPT). Shampoos had to be used 2-3 times a week for 6 months. Hair shedding during shampoo was evaluated semiquantitatively. Hair density on the vertex was evaluated on photographs using a Dermaphot. Trichograms were used for determining the anagen hair percentage and the mean proximal hair shaft diameter using computerized image analysis. The sebum excretion rate (SER, mug cm(-2) h(-1)) was also measured using a Sebumeter((R)). The three treatments cleared pruritus and dandruff rapidly. At end point, hair density was unchanged, although hair shedding was decreased (KTZ: -17.3%, PTO: -16.5%, ZPT: -10.1%) and the anagen hair percentage was increased (KTZ: 4.9%, PTO: 7.9%, ZPT: 6.8%). The effect on the mean hair shaft diameter was contrasted between the three groups of volunteers (KTZ: 5.4%, PTO: 7.7%, ZPT: -2.2%). In conclusion, telogen effluvium was controlled by KTZ, PTO and ZPT shampoos at 1% concentration. In addition, KTZ and PTO increased the mean hair shaft thickness while discretely decreasing the sebum output at the skin surface. [less ▲]