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Skin types
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Although skin may seem more or less smooth to the touch, it does have a structure, called micro-relief. This relief reveals a network of triangles and diamond shapes dotted with hair follicle and sebaceous gland openings. At higher magnification you can see pearls of sweat, the film of sebum and desquaming corneocytes.
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Scanning electron microscopy of normal skin
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Normal skin is soft to the touch, uniform and without obvious imperfections. It can sometimes be greasy and shiny in the "T zone" formed by the forehead, the nose and the chin, it then is called mixed skin. There is no excessive production of sebum. Micro-relief is characteristic of a well-moisturized skin and neither secretes too much sweat nor too much sebum
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Scanning electron microscopy of oily skin, with sebum and sweat drops
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Oily skin is characterised by the abundance and nature of the sebum excreted at the skin surface by the sebaceous gland, target organ of androgens. It is most frequently encountered in adolescents and young adults. Excess of sebum gives the skin a shiny appearance, particularly on the forehead, the sides of the nose and the chin. In severe cases, various forms of acne can develop. A oily skin is thick, well moisturized and covered with a protective oily film. It is less sensitive to external factors, to drying out and stress and for this reason is less subject to wrinkles and signs of ageing.
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Dry skin with desquaming corneocytes
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A dry skin lacks either lipids or water or both. Other factors may also be important like ultraviolet irradiation, pollution or climatic conditions. When dryness is due to the lack of sebum, there are less protective lipids and skin is more reactive to aggressive factors. It will become wrinkled sooner than the other types of skin. People with dry skin experience a feeling of tautness after washing. Adult/dry skin is also encountered in elderly people who suffer a loss of elasticity and visible signs of ageing caused by the slowing down of epidermic renewal. Dehydrated dry skin is associated with a significant lack of moisture. The most obvious characteristic is certainly a coarse feel and roughness of the cutaneous surface, sometimes accompanied by irregular desquamation or chapping. It may be a question of constitution, as is often the case with pale, thin, delicate skins, with a tendency to suffer from eczema or to be sensitive to the cold (tendency to chapping) or to dryness from the ambient air causing tautness and itching to various degrees.
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