Emmanuelle Uhoda

The Conundrum of Skin Pores in Dermocosmetology

‘Skin pore’ is a term used by lay people and in the field of cosmetology. It remains misleading when it is not clearly defined. Indeed, lay people use it with at least 3 different meanings. Basically, invisible pores represent the openings of the sweat gland apparatus. By contrast, the visible pores represent enlarged empty funnel-shaped or cylindrical horny impacted openings of pilosebaceous follicles. This review describes some of the current objective methods used to describe skin pores.

Silicon image sensor technology for in vivo detection of surfactant-induced corneocyte swelling and drying

Background: Several instrumental methods can indirectly assess some specific aspects of cutaneous irritation at the level of the stratum corneum (SC). Objective: There is a need for developing more sensitive approaches in this field. Methods: We assessed a recently introduced innovative tool (SkinChip®) based on capacitive pixel-sensing technology in its potential to detect early discrete manifestations of skin irritation. The sensor generates a detailed non-optical picture corresponding to a capacitance map of the skin surface reaching 50 µm pixel resolution. Some topographical details can be easily disclosed and the SC hydration as well. Two surfactant solutions were tested on volunteers. These solutions were applied under test patches for 2 days on the volar forearms. Clinical and SkinChip assessments were performed 3 h after removing the patch. Results: The generated images allowed a precise observation of skin irritation which appeared as a two-step process. Early changes consisted of darker pixels corresponding to overhydrated swollen corneocytes at the irritated sites. Two days later, the same area appeared as white pixels, indicating the loss of corneocyte hydration. Conclusion: The SkinChip device appears to be a very sensitive tool for detecting the early steps of surfactant-induced skin irritation affecting the SC.

Repair kinetics of stratum corneum under repeated insults.

Background: The stratum corneum (SC) structure and functions are altered by surfactants. Enhancing the repair mechanisms is a goal for some skin care formulations. Aim: To design an experimental procedure allowing the discrimination of repair efficacy for topical products applied to threatened SC. Method: Controlled SC strippings followed by repeated forearm soak sessions in surfactant solutions were used to compromise the SC barrier function in 20 volunteers. Two test formulations were compared. They were applied twice daily for 2 weeks before initiating the SC damages, and for the next 2 weeks while sustaining the procedure of soak sessions. Daily assessments involved objective measurements of parameters including transepidermal water loss, the value of the passive sustainable SC hydration and the epidermal turnover rate using the dihydroxyacetone test. Result: The experimental procedure allowed to clearly distinguish the differences in the kinetics of SC repair between the topical formulations. In the present study design, the repair of the barrier function mirrored the SC renewal. Conclusion: The present experimental design slows down the repair rate of the SC barrier function. Thus, it increases the sensitivity of biometrological measurements assessing some of the major SC properties. It also better mimics the common in vivo situation experienced by subjects chronically exposed to irritant xenobiotics.

Irritation cutanée et vitesse de propagation d'ondes ultrasonores

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.

Comparative Clinical and Electrometric Assessments of the Impact of Surfactants on Forearm Skin

Surfactant-based skin care products can induce minimal to severer alterations of the human stratum corneum (SC). These changes can be conveniently assessed using electrometric devices. Four different surfactant-based solutions were applied to the forearms of 10 healthy volunteers following a soap chamber test method. The 2-day patch testing was followed by a 2-week follow-up. Clinical and instrumental assessments were performed at 7 time points. Data generated by the Corneometer® CM820, the Dermalab Moisture Module® and the Nova Dermal Phase Meter® (DPM) 9003 were compared. The significant differences between the product aggressiveness to the SC were similarly disclosed by the Corneometer and the Dermalab Moisture Module. The ranking of product aggressiveness given by the 3 devices 5 days after patch removal was similar to that given by the clinical assessment of erythema. A high level of correlation was found between the values yielded by the immediate and continuous mode assessments using the Dermalab Moisture Module with the pin probe, while the correlation was weaker with the Nova DPM. This finding may be related to the fact that the Nova DPM is influenced by the accumulation of the transepidermal water loss in the continuous mode assessment while there is no significant occlusion effect of the Dermalab Moisture pin probe that is more representative of the initial level of SC hydration. In conclusion, the Corneometer and the Dermalab Moisture Module respond similarly to changes in the SC content. This finding is different from some previous reports.

Ultraviolet light-enhanced visualization of cutaneous signs of carotene and vitamin A dietary deficiency.

Abstract Dietary deficiencies are multiple and some of them may induce specific changes in the skin biology and structure. Vitamin A defi ciency is well identifi ed as a cause of xerosis and follicular keratosis. Skin of the forehead and balding scalp was examined in 3 homeless alcoholic men who suffered from altered liver functions and denutrition including carotene and vitamin A deficiencies. The ultraviolet light-enhanced visualization (ULEV) method was used with a computer-assisted video camera equipped with an internal ultravioletemitting unit. Twenty healthy age-and phototype-matched men served as controls. Subclinical alterations of the stratum corneum and tiny follicular horny spikes at the skin surface were disclosed by ULEV. They were consistent with discrete flakiness on the forearms. By contrast, skin of the face and scalp showed follicular horny impactions corresponding to kerosis without any evidence for interfollicular xerosis. The skin condition was markedly improved after a 10-week dietary normalization. It is concluded that the ULEV method reveals some of the mildest and subclinical skin changes secondary to carotene and vitamin A deficiency. It could tentatively be used as a cheap and non-invasive aid in clinical screening programs among populations at risk.

Coping with mild inflammatory catamenial acne A clinical and bioinstrumental split-face assessment

Background: Acne is a multifactorial disease exhibiting distinct clinical presentations. Among them, the catamenial type is a matter of concern for young women. Some oral contraceptives may help without, however, clearing the skin condition.

Effect of residence time on the efficacy of antidandruff shampoos

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.

Quantification of dandruff adherence to hair.

Dandruff adherence to hair shafts is a visible annoying phenomenon. The aspect can be recorded by different means including the ultraviolet light‐enhanced visualization (ULEV) method and microscopy. We present another quantitative method. Hairs were clipped from the parietal scalp area of 25 volunteers complaining of dandruff. They were firmly applied onto cyanoacrylate‐coated microscopic slides. Hairs were lifted up after 15–20 s leaving a cast in the adhesive coat. Dandruff were thus harvested from the hair shafts and remained attached to the cyanoacrylate coat. After staining, the material was submitted to image analysis to derive the dandruff density per unit length of hairs. In 11/25 subjects, a correlation was found between the width of the hair casts and the dandruff density. This method does not collect all dandruff along hair shafts, but data are likely representative of the whole corneocyte load.

Responsive corneosurfametry following in vivo skin preconditioning

Skin is subjected to many environmental threats, some of which altering the structure and function of the stratum corneum. Among them, surfactants are recognized factors that may influence irritant contact dermatitis. The present study was conducted to compare the variations in skin capacitance and corneosurfametry (CSM) reactivity before and after skin exposure to repeated subclinical injuries by 2 hand dishwashing liquids. A forearm immersion test was performed on 30 healthy volunteers. 2 daily soak sessions were performed for 5 days. At inclusion and the day following the last soak session, skin capacitance was measured and cyanoacrylate skin‐surface strippings were harvested. The latter specimens were used for the ex vivo microwave CSM. Both types of assessments clearly differentiated the 2 hand dishwashing liquids. The forearm immersion test allowed the discriminant sensitivity of CSM to increase. Intact skin capacitance did not predict CSM data. By contrast, a significant correlation was found between the post‐test conductance and the corresponding CSM data. In conclusion, a forearm immersion test under realistic conditions can discriminate the irritation potential between surfactant‐based products by measuring skin conductance and performing CSM. In vivo skin preconditioning by surfactants increases CSM sensitivity to the same surfactants.