题型：阅读理解 题类：常考题 难易度：普通
辽宁省辽阳市2017-2018学年高一下学期英语期末考试试卷
It is generally believed that humans can't live without sleep. As any person suffering from lack of sleep knows, dark circles under the eyes usually stand out after a bad night's sleep.
But why do people get these dark eye bags? The answer is both genetic (that is, relating to your DNA) and environmental (a result of your everyday living, such as rubbing your eyes or getting too little sleep), said Dr. Carol Clinton, a skin-care researcher in Dublin, Ohio.
But “the biggest reason is genes,” Clinton told Live Science. Eye bags are generally more noticeable in people who, because of genes, have thin or pale skin. When people are tired or very nervous, blood circulation in the eye area becomes slow, allowing blood to pool there, Clinton said. Capillaries（毛细血管）stand out, leading to dark eye circles, she said.
Besides, eye bags result from eyes' fat moving forward. An age-connected increase in fat beneath the eyeballs leads to eye bags. “Anyway, when your eyes' fat is moving forward, you may think about having an operation in that area,” Clinton said, “A person can get 9 hours of sleep a night, but still have eye bags because of a genetic development.”
In other cases, environmental problems cause eye bags. For example, allergies（过敏）—especially seasonal allergies—can cause capillaries to stand out. Getting too much sun can also damage and thin the skin, making dark circles under the eyes easy to see. Besides, eating salty foods can cause the body to hold more water, which makes eye bags worse, according to the Mayo Clinic.
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