The lips are different from other tissues of the human body. The lips are a transition tissue, an evo- lutionary combination of the facial skin and of the buccal membrane. This combination is unique, since, unlike the skin or the mouth, the lips do not have a natural defense mechanism. The only protection comes from the touch of saliva by means of the tongue or pressing the lips against each other against an external threat. The transactional nature of the lips suggest that, anatomically speaking, the lip area does not enjoy the complete functionalities, as is the case of the epidermis or the buccal mucosa. Since the thickness of the stra-
turn corneum (the outermost layer of the skin) is thinner and the number of keratinized cells is smaller, the lips have a reduced effective natural protection, but a higher absorption capacity. However, any active ingredient present in products for lips, should have a substantial absorption. The lip tissues do not have a moisturizing capacity due to the non-existence of sebaceous or salivary glands. For this reason, the lip tissues are subject to natural dryness. In spite of this, moisture can be applied to the lips if the lip product contains active substances that stimulate the regeneration of the cells and that maintain water under the surface of the lips. There is little or no melanin in the lip tissues. This means that there will be less or no absorption of ultraviolet rays (UV), which entails a greater susceptibility to damages to the cells.
The lip tissues have vascularization close to the surface, creating a red or pink color. This superficial vascularization also produces a stronger impact on the metabolism of the surface cells.
The lips also have a large number of nerve endings. This means a superior sensitivity to dryness or damages. The lips are subject to several of diseases, which require the use of safe unctuous raw materials for the development of a formula. Some of the most common complaints about the lips are: dryness, cracked lips, redness and cracking, aphthae, lip cancer and lip wrinkles.
Dryness and cracking are related with the loss of natural moisture of the lips. Redness and cracking are due to a sensitivity reaction of chemical products and pollutants. Aphthae or fever blisters are clinically re- lated with the herpes simplex virus, being caused by a drop in the immune system and due to sunburns, excess dryness, disease and stress. The exposure to sunlight may cause folds on the lips. The treatment requires hydration and restoration of glycosaminoglycans, together with natural collagen.
Since the lips are one of the parts of the body that are most ex- posed to external aggressions and also because they have a different texture from the rest of the skin, they require special care. The great enemies of the lips are: sunlight, wind, cold, that is to say, in any season of the year or at
any temperature there is a great possibility of the lips becoming parched.