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The Oxford Dictionary defines feel as “to be aware of a person or object through touching or being touched” and “experience (an emotion or sensation).” This word connects the skin and the brain, which both develop from ectoderm in the embryo and play a similar role of a biosensor interface. They maintain body homeostasis by processing environmental information and releasing appropriate hormones and mediators.
The skin is the human body’s biggest sensory organ—the organ of touch that helps humans make and feel physical contact. There is bidirectional reciprocity, as one cannot be touched without touching. The skin is intimately tied to human emotions, with individuals feeling out of touch and letting things get under their skin. Humans blush with embarrassment, are flushed with pride, turn white with fear, pale with grief and green with envy.1 Life experiences that “touched us” are etched on human skin in the form of lines and wrinkles.
The feel good factor in skin care stems from the integrity of the skin barrier. A recent theory hypothesizes that the injured epidermis can affect emotional state and act on the brain, which this author supports based on client feedback.2 Epidermal keratinocytes have sensory systems and play an active role in the maintenance of barrier function. They produce bioactive molecules, i.e., cytokines, neuropeptides, oxytocin and glucocorticoids, in response to barrier impairment or insult such as environmental dryness or UV radiation to regulate skin physiology and emotional condition. Those with skin conditions associated with impaired epidermal barrier have reported itching, sleep disturbance and appearance anxiety. Dermatologists have found a link between the severity of atopic dermatitis and the level of patients’ depression or anxiety; fatigue and depression have been reported in patients with psoriasis. Plasma cytokines and glucocorticoids are associated with depression, and oxytocin is involved in behavior and social bonding. The deterioration of skin barrier function can cause a depressed mental state and vice versa, creating a vicious cycle.2
Stress is known to delay the skin barrier recovery3, 4 and stress-reducing interventions show improved rates of healing in psoriasis.5, 6 The quality of intimate relationships can also influence the skin barrier. A recent study examined a link between self-reported attachment and skin barrier recovery in young dating couples in satisfied relationships. Greater attachment anxiety predicted faster skin barrier recovery in women and slower skin barrier recovery in men.7
The feel good factor, a positive impact of cosmetics on well-being, can be quantified by quality of life (QoL) questionnaires. L’Oréal and Data Mining International published a validation study of BeautyQol, a questionnaire developed to assess the impact of cosmetic products and physical appearance in healthy adult populations across the world. The questionnaire measured social life, self-confidence, mood, energy and attractiveness.8
Science and Applications of Skin Delivery Systems bridges the gap between the two extremes of all-science and all-systems books. This book was written by experts who know the potentials as well as the limitations of the delivery systems.Science and Applications of Skin Delivery Systems and Skin Barrier: Chemistry of Skin Delivery Systems