Splinter hemorrhages

Splinter hemorrhages are thin streaks of blood beneath a fingernail or toenail. They are named for their resemblance to tiny wooden splinters. The blood comes from small vessels in the nail bed, which is the skin underneath the hard nail plate.

Most splinter hemorrhages result from minor injury. You might notice one after catching a nail, wearing tight shoes, biting your nails, or having a manicure. Less often, repeated or unexplained marks can be linked to a nail condition, inflammation, or an illness elsewhere in the body.

The marks themselves are usually harmless and do not need to be removed. Their pattern, associated symptoms, and whether they grow out with the nail can help show whether further assessment is needed.

A splinter hemorrhage usually looks like a narrow red, reddish-brown, or black line running in the same direction as the nail. It may be only a few millimetres long. There may be one streak or several.

The mark is usually painless. If it followed an injury, the nail or fingertip may also feel tender. Unlike blood near the surface of the skin, the line generally does not fade when pressed because it is trapped beneath the nail plate.

A trauma-related mark often appears toward the tip of the nail. As the nail grows, it should move toward the tip and eventually be clipped away.

Not every dark nail line is a splinter hemorrhage. Pigment can also create a brown or black band. A new band that becomes wider, has irregular colouring, changes the nail, or spreads onto nearby skin should be examined.

Minor injury is the most common cause. The injury may be so small that you do not remember it. Common triggers include nail biting, picking beneath the nail, manicures, sports, repetitive hand work, and pressure from tight footwear.

Nail conditions can make the nail bed easier to injure. Psoriasis may cause nail pitting, lifting, thickening, or colour changes as well as splinter hemorrhages. A fungal nail infection may cause thick, brittle, discoloured nails.

Less common causes include inflammation of small blood vessels, called vasculitis, and some conditions that affect blood clotting or connective tissues. Certain medicines may also be associated with nail changes. Do not stop a prescribed medicine because of a nail mark; ask the prescriber if you are concerned.

Infective endocarditis, an infection of the heart's inner lining or valves, can cause splinter hemorrhages. However, splinter hemorrhages alone do not mean that you have this infection. Endocarditis usually causes other symptoms, such as fever, chills, marked tiredness, breathlessness, or feeling generally unwell.

Arrange a routine appointment if the marks:

• Keep returning without a clear injury
• Affect several nails
• Begin close to the base of the nail
• Do not move toward the tip as the nail grows
• Occur with nail thickening, pitting, lifting, pain, or swelling
• Look more like a widening or irregular dark band

Seek same-day medical advice if new, unexplained splinter hemorrhages occur with fever, chills, night sweats, unusual fatigue, or feeling significantly unwell. This is particularly important if you have an artificial heart valve, known valve disease, a previous episode of endocarditis, or a recent bloodstream infection.

Call emergency services for severe difficulty breathing, chest pain, fainting, sudden confusion, or signs of a stroke such as facial drooping, arm weakness, or trouble speaking. These symptoms require emergency care whether or not nail marks are present.

A healthcare professional will ask when the marks appeared, whether there was an injury, and whether they are changing as the nail grows. They may ask about work, sports, footwear, manicures, skin conditions, medicines, fever, and heart history.

The nails, fingertips, skin, and sometimes joints will be examined. A magnifying tool called a dermatoscope may help distinguish dried blood from nail pigment.

Tests are not always needed when there is an obvious injury and a single mark is growing out normally. If a fungal infection is possible, a nail clipping or scraping may be tested. Blood tests may be considered when several nails are affected or there are symptoms of inflammation or infection.

If endocarditis is suspected, assessment may include blood cultures, which look for germs in the blood, and an echocardiogram, an ultrasound scan of the heart.

The streak itself usually needs no treatment. It cannot be washed away, and trying to scrape or pierce the nail may cause further injury or infection. The trapped blood should move outward as the nail grows.

You can reduce further nail injury by keeping nails neatly trimmed, avoiding biting or picking, and wearing well-fitting shoes. Gloves may help if your work repeatedly knocks or presses on your nails. Be gentle with manicures and avoid cutting deeply around the cuticle.

Taking a clear photograph can help you track whether the mark is moving. If possible, leave the nail free of dark polish before an appointment so it can be examined easily.

Treatment for an underlying nail or medical condition depends on the diagnosis. Do not use antifungal treatment or antibiotics like amoxicillin or doxycycline unless a healthcare professional confirms that they are appropriate.

A trauma-related splinter hemorrhage usually travels toward the tip as the nail grows and disappears when that part is clipped. This may take weeks or months. Toenails grow more slowly than fingernails.

The mark should not spread backward toward the nail base. New lines can appear if pressure or injury continues. Marks that remain fixed, repeatedly return, or affect several nails deserve medical review.

Are splinter hemorrhages always a sign of endocarditis?

No. Minor nail injury is much more common. Endocarditis becomes a concern mainly when unexplained marks occur with fever, feeling unwell, relevant heart conditions, or other signs of infection.

Can I remove the blood from under the nail?

Usually not, and removal is unnecessary. Scraping or puncturing the nail can damage the nail bed. Let the mark grow out naturally.

Why do I have one when I do not remember an injury?

Everyday pressure can damage tiny nail-bed vessels without causing noticeable pain. Examples include typing, sports, household work, nail biting, or pressure from shoes.

What if the line does not move as my nail grows?

Book an appointment. A fixed dark line may not be trapped blood and may need closer examination, especially if it widens, changes colour, or extends onto the surrounding skin.