Sebaceous gland activity has four distinct components which are sebum production (a secretion rate function), storage (a volume function), surface output (a delivery rate function) and stratum corneum permeation (an influx rate function). The oily appearance of skin results from an excess of sebum excretion and spreading over the body surface and its interaction with the skin surface. A multi-pronged approach is often useful to assess skin greasiness with precision. The clinical evaluation of skin greasiness and its shiny appearance should be further complemented by quantifying the large pores, follicular plugs and comedones. The sebum amount present at the skin surface can be measured non-invasively using one of several methods based on solvent extraction, cigarette paper pads, photometric assessment, bentonite clay and lipid-sensitive tapes. Quantitative parameters include the sebum casual level, the sebum excretion rate, the sebum replacement time, the instant sebum delivery, the follicular excretion rate, the density in sebum-enriched reservoirs and the sustainable rate of sebum excretion. A series of environmental and biological features influence the data. Hence rigorous methodological designs are mandatory to support claims. As a rule, accuracy of the methods is adversely affected by skin temperature, degree of hydration and surface roughness. An additional confounding factor is the inherent difficulty of collecting the surface lipids without a contribution from the follicular reservoir. A better understanding of factors that alter the sebum amount at the skin surface may well assist in the development of sebosuppressive agents to help the reduction of the skin greasiness and improve acne.

‘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.

SynopsisDandruff 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. Ré suméL'état pelliculaire est une affection commune du cuir chevelu atteignant près de la moitié de la population des individus post-pubères, quels que soient leur ethnie et leur sexe. Cette affection peut s'avé-rer rebelle chez certains. La biocénose cutanée, en particulier la flore des Malazzezia spp., joue un rôle étiologique clé, de même que la capacité particulière exprimée par certains cornéocytes de pouvoir se couvrir de ces levures. De nombreux arguments convergent pour affirmer que les kératinocytes jouent un rôle actif dans la génération et l'expression de réactions immunopathologiques. C'est vraisemblablement le cas dans l'état pelliculaire. Lors de la stimulation par une colonization critique de cornoècytes par les levures Malassezia, la liberation de médiateurs pro-inflammatoires est accrue. Cela conduirait à la micro-inflammation infraclinique des pellicules. Dans la dermite séborrhéique, les dépots locaux d'immunoglobulines et la libération de lymphokines seraient responsables du recrutement et de l'activation locale de leucocytes aboutissant à une amplification éventuelle de la réaction inflammatoire. Certaines causes accessoires nonmicrobiennes des pellicules peuvent intervenir par le biais d'irritants physiques ou chimiques. De nombreuses méthodes d'évaluation des pellicules ont èté décrites. Dans notre laboratoire, l'examen clinique et la squamométrie sont nos outils favoris. Les pellicules peuvent précipiter un effluvium télo-gène et exacerber une alopécie androgénétique. Des formulations antipelliculaires possédant une

Skin microrelief alters progressively with age. Wrinkles do not result from these changes but are superimposed upon them. Wrinkles result from structural changes in the epidermis, dermis and hypodermis. Four types of wrinkles can be recognized. Type 1 wrinkles are atrophic. Type 2 wrinkles are elastotic. Type 3 wrinkles are expressional. Type 4 wrinkles are gravitational. Each type of wrinkle is characterized by distinct microanatomical changes and each type of wrinkle develops in specific skin regions. Each is likely to respond differently to treatment. Skin microrelief and skin folds can be identified on histological examination. By contrast, only minimal dermal changes are found beneath permanent or reducible wrinkles compared with immediately adjacent skin. A series of objective and non-invasive methods is available to quantify the severity of wrinkling.

This review addresses the current concepts about dandruff. The nature, origin and treatments of such skin conditions are scrutinized. The role of Malassezia spp. and other triggering factors is highlighted.