Fragility of epidermis in newborns, children and adolescents.

Within their first days of life, newborns' skin undergoes various adaptation processes needed to accommodate the transition from the wet uterine environment to the dry atmosphere. The skin of newborns and infants is considered as a physiological fragile skin, a skin with lower resistance to aggressions. Fragile skin is divided into four categories up to its origin: physiological fragile skin (age, location), pathological fragile skin (acute and chronic), circumstantial fragile skin (due to environmental extrinsic factors or intrinsic factors such as stress) and iatrogenic fragile skin. Extensive research of the past 10 years have proven evidence that at birth albeit showing a nearly perfect appearance, newborn skin is structurally and functionally immature compared to adult skin undergoing a physiological maturation process after birth at least throughout the first year of life. This article is an overview of all known data about fragility of epidermis in 'fragile populations': newborns, children and adolescents. It includes the recent pathological, pathophysiological and clinical data about fragility of epidermis in various dermatological diseases, such as atopic dermatitis, acne, rosacea, contact dermatitis, irritative dermatitis and focus on UV protection.

In vitro approaches to pharmacological screening in the field of atopic dermatitis.

In vitro models are valuable for evaluating potential active ingredients and other molecules used in medications for atopic dermatitis (AD). However, finding appropriate in vitro models can be problematic. Our strategy was to set up different in vitro models that would mimic the pathomechanisms of AD. We describe five such models - the AD keratinocyte model, the AD reconstructed human epidermis model, the adaptive immunity model, the innate immunity model and the pruritus model - which we have used to evaluate a new ingredient for emollients derived from a biological extract. The models chosen provide useful data for the pharmacological characterization of active ingredients in adjunctive treatments for AD.