終於明白自己是怎麼回事了：皮膚劃痕症！

怪不得總是全身莫名發癢！而且越搔越癢！有一次手賤抓了幾下，結果癢到失眠。

但是我劃一下皮膚不會立即起劃痕，而是要等上三五分鐘。我以前以為大家都這樣…

末尾附圖，請謹慎決定要不要看。

下面貼上中英文維基百科：

「單純性皮膚劃痕症」，即用物件劃皮膚後，出現一道道的蕁麻疹，但患者並沒有瘙癢感覺和其它不適，風疹塊一般會在15至20分鐘後會自行消退。這屬於正常人生理性的體質異常反應，約5%正常人有此現象。

「癥狀性皮膚劃痕症」，同樣當皮膚受到物件刺激後，人體的肥大細胞會釋放出組織胺等活性物質，這些物質能引起皮膚的毛細血管擴張，血漿從血管中滲出到真皮，而出現皮膚髮癢和風團塊。

有些患者則是由於免疫球蛋白E所介導而產生的，患這種皮膚劃痕症的人經常無緣無故地覺得皮膚髮癢，於是用指甲抓撓或用鈍物擦劃皮膚，就出現一條條紅斑風團，接著風團便水腫高出皮面，並在紅斑風團的邊緣部位出現紅暈現象。

Dermatographic urticaria (also known as dermographism, dermatographism or "skin writing") is a skin disorder and one of the most common types of urticaria affecting 2–5% of the population.

This weak membrane easily and rapidly breaks down under physical pressure causing an allergic-like reaction, in general a warm red wheal (welt) to appear on the skin. It can often be confused with an allergic reaction to the object causing the scratch, when in fact it is the act of being scratched that causes a weal to appear. These wheals are a subset of urticaria (hives) that appear within minutes, in some cases accompanied by itching. The first outbreak of urticaria can lead to others on body parts not directly stimulated, scraped, or scratched. In a normal case, the swelling will decrease with no treatment within 15–30 minutes, but, in extreme cases, itchy red welts may last anywhere from a few hours to days.

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