Читать книгу Cosmeceuticals - Группа авторов - Страница 35

Cosmeceuticals must be designed to meet the unique anatomy and physiology of the face. The face begins at the anterior hairline, stops at the ears, and is bounded by the lateral jaw line and chin. It is the most complex and challenging area of the body for the formulator, containing all of the glandular structures of the body, including hair, characterized by dry transitional skin found around the eyes, nose, and mouth. Facial skin is the thinnest on the body, except for that around the eyelids, making it the most susceptible to irritation and allergy, a challenge for the cosmeceutical formulator. The face is also characterized by numerous follicular structures in the form of pigmented terminal hairs in the eyebrows, eyelashes, and male beard combined with white fine downy vellus hairs over the rest of the face. These follicular structures are the transition between the skin on the surface of the face and the ostia, which create interesting facial topography consisting of mountains around each follicular structure with intervening valleys constituting the facial dermatoglyphics.

The skin lining of the pore connecting the surface to the depth of the follicle is an important transitional area. It is the site of irritation resulting in a follicular irritant contact dermatitis causing the “breakouts” associated with cosmetics. The elimination of all irritants from cosmeceutical formulations is important to prevent this acneiform eruption. In the longer term, it is important that perifollicular irritation and occlusion does not occur, otherwise inflammatory papules and/or comedones may result. Cosmeceuticals should be tested to be sure they are noncomedogenic and nonacnegenic.

Cosmeceuticals must also improve the condition of the skin by optimizing the barrier. This is actually the major benefit of cosmeceuticals. An intact barrier is smooth and soft and able to reflect light and create the appearance of luminous skin, which is considered younger, more attractive skin. Cosmeceuticals contain a variety of ingredients, including emollients and polymers, to create this enhanced light reflection; however, this is truly an appearance benefit that will be lost when the cosmeceutical is removed from the skin surface. Cosmeceuticals can also improve the skin barrier functionally. Enhanced organization of the intercellular lipids, composed of sphingolipids, free sterols, and free fatty acids [1], and corneocytes will optimize skin behavior and appearance simultaneously [2]. Thus, the moisturizer vehicle of cosmeceuticals is a very important part of perceived efficacy.