What causes a splinter hemorrhage to appear on a nail?

Reviewed by Yoshinori Abe, MD

Internal Medicine

Splinter hemorrhages are thin, reddish-brown lines that appear under the fingernails or toenails. They are most often caused by minor trauma to the nail, such as bumping or pinching it. In some cases, they appear without a clear cause. Less commonly, they can signal an underlying condition like endocarditis, vasculitis, or psoriasis.

Because splinter hemorrhages can range from harmless to a sign of something more serious, it's worth understanding what's behind yours before assuming it's nothing—or panicking that it's serious. A free, instant, online symptom check can help you quickly assess your risk factors, identify possible causes, and decide whether a doctor's visit is needed. It takes just a few minutes and could save you hours of worry or unnecessary appointments.

Reviewed for medical accuracy: 07/15/2026

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Explanation

Splinter hemorrhages are small lines of blood under the nails that look like splinters. These can happen because of small injuries to the nail, like bumping it against something hard. Sometimes, they appear without any clear reason, which is called idiopathic.

Causes of Splinter Hemorrhages

Trauma: According to the medical literature, trauma to the nail is a common reason for splinter hemorrhages. This can include injuries from everyday activities or specific sports-related injuries.
Idiopathic: Some splinter hemorrhages occur without any clear cause, which is known as idiopathic. This means they appear without a direct injury or underlying health problem.

Understanding these causes can help in recognizing why these marks appear on the nails. If you see these marks and are unsure why they appeared, you can use Ubie's free AI symptom checker to help identify potential causes and determine if you should seek medical attention.

(References)

Haber R, Khoury R, Kechichian E, & Tomb R. (2016). Splinter hemorrhages of the nails: a systematic review .... International journal of dermatology, 27420914.
Saladi RN, Persaud AN, Rudikoff D, & Cohen SR. (2004). Idiopathic splinter hemorrhages. Journal of the American Academy of Dermatology, 14726890.
Mortimer PS, & Dawber RP. (1985). Trauma to the Nail Unit Including Occupational Sports .... Dermatologic clinics, 3830505.

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