Everyone has a unique genetic profile. No two of us are exactly alike, with the exception of identical twins. The characteristics of your skin –its color and pore size, how much hair you have and where you have it, and how much sebum and sweat coats your skin –are dictated by your genes. Your skin characteristics may be similar to your father’s skin or your sisters but there are going to be important differences. After all, the medicines you take, where you live, the stress you experience are unique to you. Even identical twins are exposed to different environmental influences. And your own skin will not be the same tomorrow as it is today.
When people think of skin type, they typically mean how oily or dry the skin is. Oily is actually a white, fatty, sticky, substance secreted by the sebaceous glands. Except for the lips and eyelids, which have no hair follicles or sweat glands, sebaceous glands empty sebum into the upper part of the hair follicle. As the oil emerges from the follicle opening, or pore, it lightly coats the skin, mixing with the structural lipids within the stratum corneum, creating a kind of protective barrier that keeps water within the layers, helping the skin stay moist and soft.
When the sebaceous glands are overactive, the excess sebum can make skin look shiny or feel greasy. When sebaceous glands are underactive or harsh chemicals or overzealous scrubbing remove the natural lubricant, moisture is lost and the skin becomes dry.
Using sebum and structural lipids, or oil, as primary criteria, the skin types are broadly categorized as oily, dry, or normal/combination. It is normal for pores to be more abundant on the nose and chin, and so there is more oil secreted in these areas, the so called T-zone. There are fewer pores on the cheeks and around the eyes, so these normally tend to be drier.
The pores of your skin are medium-size. Although you may have more pores along your nose and chin, and these areas may be oilier than your cheeks and around your eyes, you are not troubled with blackheads and pimples. Your complexion is bright and it feels smooth to the touch. Your skin is usually free of blemishes and tolerates extremes in temperatures well. Your cheeks may redden in the cold, but they don’t become irritated and chapped. Makeup stays where you put it and doesn’t flake. Weather conditions may change your skin: it’s a bit oiler when it’s warm and drier when it’s cool.
In a sense, dry skin is like a dry sponge. It rough, hard, and has little cracks in it. When the sponge is soaked in water, it becomes plump, soft, and smooth, and those little cracks disappear. Dryness is caused by lack of either sufficient sebum or structure lipids or both. So if you have dry skin, it may be because your oil glands are not producing enough sebum, or aging has taken a toll on the production of structural lipids within and outside of your skin cells, or because you are cleansing your skin too aggressively or too often. Sometimes the wrong foundation or face powder can be drying. Whatever the reason, the lack of moisture disturbs the skins barrier function.
|Article by Howard Murad, M.D., FAAD, a world renowned skincare expert and founder of the Inclusive Health movement. Read more about Dr. Murad.|