This Is What Really Causes Red And Black Spots On Fingernails

Getting your finger caught in a door or smashed by a hammer blow can happen to anyone. This type of injury typically causes bruising that can discolor a fingernail. But if you ever detect red or black spots on the fingernails, pay attention: That form of discoloration may be a symptom of a potentially serious underlying health issue. If red or black spots appear under your fingernails, you should seek medical attention right away.

When thin, red or reddish-brown streaks appear under the fingernail, this could be a splinter hemorrhage, according to MedlinePlus. Splinter hemorrhages can be caused by a physical injury, but they also might be a sign of serious heart or circulatory problems. LIkewise, black spots that show up under the fingernails can be signs of bruising, but potentially could be related to a rare form of cancer called subungual melanoma (per MedicalNewsToday).

What do lines running down the nails mean?

Splinter hemorrhages — so named because of their unique shape — are thin lines that are red in color and run down the lines of the nail like a splinter. They are common in people with inflammatory skin diseases like eczema and psoriasis, according to ScienceDirect. But multiple splinter hemorrhages appearing in the same nail can be a sign of more serious health issues like endocarditis (infection of the heart valves) or vasculitis (swelling of blood vessels).

Endocarditis is a dangerous condition that is usually caused by an infection that has spread through your bloodstream to your heart, and if it is not treated quickly it could be life-threatening (via MayoClinic). The causes of vasculitis are not fully understood, although it appears to be an auto-immune disease (per VasculitisFoundation). If undiagnosed and untreated, it too can lead to a potentially fatal outcome, including blood clots, organ failure, and aneurysm. For these reasons, red discoloration underneath the fingernails, especially red lines, should be brought to the attention of a medical professional. 

Black spots on your fingernails should be looked at

A dark brown or black spot or streak that appears in the nail could be cause for serious concern. According to the American Academy of Dermatologists (AAD), a particular kind of skin cancer called subungual melanoma usually presents as a dark streak under the nail or a dark patch of skin right next to your nail. If your nail actively splits near the dark spot, or if the nail lifts off the nail bed, this might be a warning sign of advanced subungual melanoma.

Subungual melanoma accounts for 0.7 to 3.5% of all malignant melanomas worldwide (via Stat Pearls Publishing). More than 75% of subungual melanomas show up on either the thumb or big toe. This type of cancer is more common in people over the age of 50 and those of African, Asian, or Native American descent who tend to have more skin pigment and therefore more protection against skin cancer everywhere but under the nails.

Because subungual melanoma is often diagnosed much later than other forms of malignant melanoma, it is often much deadlier (via AAD). For this reason, dark or black spots under the fingernails should be examined by a doctor or dermatologist.