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Skin Care and Diseases

Streak of black fingernail



My 7 months old baby boy has got a streak of black fingernail on his right thumb. The black streak runs from base to tip. This started only when he was around 2 - 3 months old, was not like that when he was newborn. I am quite sure he didn`t hurt himself like slumming into something, etc. What are the possibilities of causes?


There are many possibilities. Trauma is one of them, which I believe is what you're trying to rule out when you said he did not hurt himself against anything. A pigmented nevus on the nail bed can appear as a black streak. The most worrisome cause of black streak on fingernails is melanoma, which is unlikely in a baby. Black streaks are more common in dark-skinned individuals more than in light-skinned individuals. These are for the most part normal pigmentation and nothing alarming. Pointing it out to your doctor for a visual assessment would be good.

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Response by:

Elma D Baron, MD Elma D Baron, MD
Associate Professor of Dermatology
Director, Skin Study Center
School of Medicine
Case Western Reserve University