指甲上的白斑

Some cultures see the white spots as a good luck sign, and even call them fortune or gift spots. There's also the old idea that someone with a white spot on a fingernail is in love, or that the number of white spots equals the number of "sweethearts" a girl has. In an Alice Hoffman novel, a white spot appeared on a character's fingernail each time he lied, a telltale（迹象，指示器） sign like Pinocchio's growing nose.

But fibbing（无伤大雅的谎言） , falling in love, or winning the lottery¹ actually have nothing to do with white spots, unless you happen to hit one of your fingers in all the excitement. Dermatologists² (skin doctors) say that white spots and smeary³（油污的） streaks⁴ happen to all of us, and are usually nothing to worry about.

The official name for white nail spots is the somewhat scary-sounding punctate（点状的） leukonychia（白甲病） . (In total leukonychia, the entire nail turns white.) Kids and adults often have one or more random⁵ white dots or marks on their nails, especially if they are hard on their hands. Dermatologists say the spots appear because of repeated dings to the nail bed at the base of a fingernail (say, by a striking ball when playing sports). Much rarer causes include infections, systemic illnesses and dietary deficiencies.

White spots are a mix of keratin（角蛋白） (a tough protein) and air. The spots are places where, due to an minor⁶ injury to the nail bed, new nail cells were incompletely formed or "keratinized." The white spots will rise higher as the nail is pushed up by new growth from the nail bed. Since a nail grows about one millimeter in 10 days, it can take months for the spotted⁷ part to reach the tip for trimming off. Meanwhile, you can look at your nail spots and relive memories of all the insults and injuries to your fingers in the past year.