For starters, biting your nails can raise the risk of catching a cold or other illness because you’re putting your unwashed hands in your mouth. It can also raise the risk of paronychia, or infection of the skin surrounding the nail, says Rochelle Torgerson, M.D., Ph.D., a dermatologist at the Mayo Clinic.
Source: http://www.dentapress.com/headlines/6015-why-biting-your-nails-is-more-than-just-a-bad-habit.html
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