Red fingernails can mean anything from a minor injury to a signal that something deeper is going on in your body. The redness might appear as a flush across the entire nail bed, a thin red line running lengthwise, tiny splinter-like streaks, discoloration around the cuticle area, or a red tint to the half-moon at the base of your nail. Where the redness shows up and how many nails are affected narrows down the cause considerably.
Red Nail Beds From Everyday Causes
The most common reason for red-looking fingernails is simply increased blood flow. After exercise, a hot shower, or spending time in warm environments, the capillaries under your nails dilate and the nail bed looks pinker or redder than usual. This fades on its own and is completely normal.
Trauma is another frequent culprit. Slamming a finger in a door, repetitive tapping, or even an aggressive manicure can damage the tiny blood vessels beneath the nail. The result is a reddish or purplish discoloration that grows out with the nail over several months. If you can trace the redness back to a specific injury, it’s almost certainly this.
Splinter Hemorrhages: Thin Red Lines
If you see one or more thin, dark red or reddish-brown lines running vertically under the nail, those are splinter hemorrhages. They form when tiny capillaries in the nail bed burst and leak a small amount of blood that becomes trapped beneath the nail plate. They look like wood splinters stuck under the nail, which is how they got their name.
A single splinter hemorrhage on one nail is usually from minor trauma you may not even remember. Multiple splinter hemorrhages across several nails are a different story. Between 15% and 33% of people with infective endocarditis, a bacterial infection of the heart valves, develop splinter hemorrhages. Autoimmune conditions that inflame blood vessels, including lupus and antiphospholipid syndrome, can also cause them. If you notice these lines appearing on multiple fingers without any obvious injury, that’s worth getting checked out.
Redness Around the Nail Fold
The skin surrounding your nail, called the nail fold, can turn red and swollen from infection. Paronychia is a common nail infection that develops when bacteria or fungi enter through a break in the skin, often from biting your nails, picking at cuticles, or frequent hand washing. The skin around the nail becomes red, puffy, and tender, sometimes with visible pus.
But persistent redness around the nail folds, especially when it appears on many fingers at once, can point to autoimmune conditions. Dermatomyositis, an inflammatory disease affecting muscles and skin, causes visible changes in the nail folds in over 96% of patients. These changes include dilated blood vessels, tiny hemorrhages, and ragged, overgrown cuticles. Lupus produces similar nail fold redness, though less frequently and with fewer visible capillary changes. If you notice chronic redness and swelling around most of your nail folds along with fatigue, muscle weakness, or skin rashes elsewhere, those symptoms together paint an important picture for your doctor.
Red Streaks Running Lengthwise
A narrow red band running from the base of the nail to the tip is called longitudinal erythronychia. When it appears on just one nail, the most common cause is a benign growth called an onychopapilloma. However, this same appearance can also be caused by squamous cell carcinoma in situ, melanoma in situ, or basal cell carcinoma. Because benign and malignant causes can look identical, a biopsy is sometimes needed to tell them apart.
When red streaks appear on multiple nails simultaneously, the cause is more likely a skin condition like lichen planus or Darier’s disease, or occasionally a systemic condition like amyloidosis. A single persistent red streak on one nail that doesn’t go away deserves evaluation, since ruling out a malignancy requires a professional exam and potentially a tissue sample.
A Red Half-Moon at the Nail Base
The lunula is the pale, crescent-shaped area at the base of your nail. It’s normally white or light pink. When the lunula turns distinctly red, it can be a sign of heart failure. This change tends to appear across multiple nails and reflects underlying circulatory problems. Other conditions linked to a red lunula include chronic obstructive pulmonary disease and liver cirrhosis. If you notice your lunulas have shifted from their usual pale color to a noticeable red, particularly if you have other symptoms like shortness of breath, swelling in your legs, or persistent fatigue, bring it up with your doctor.
Lindsay’s Nails: Half Red, Half White
If the lower half of your nail appears white and the upper half looks reddish-brown or distinctly red, that pattern has a name: Lindsay’s nails. It’s associated with kidney disease. The white portion results from swelling in the nail bed tissue, while the red-brown band near the tip reflects changes in how your body handles waste products. This pattern typically shows up on most or all fingernails. A related condition, Terry’s nails, makes the nail bed look almost entirely white with a narrow reddish band at the tip, and it’s linked to liver disease.
Salmon Patches From Nail Psoriasis
Psoriasis doesn’t just affect your skin. When it targets the nails, it can create reddish, yellowish, or pinkish spots beneath the nail plate. These are called salmon patches or oil drop spots because they resemble a drop of oil trapped under the nail. The color comes from inflammation in the nail bed. You might also notice pitting (tiny dents in the nail surface), thickening, or the nail lifting away from the bed. If you already have psoriasis on your skin or scalp, nail involvement is common and worth mentioning to your dermatologist since it can indicate a higher risk of psoriatic arthritis.
Glomus Tumors: Painful Red Spots
A glomus tumor is a small, usually benign growth that forms from specialized blood vessel cells. When one develops under a fingernail, it often appears as a reddish or bluish spot visible through the nail plate. The hallmark is intense, localized pain that gets dramatically worse with cold exposure. Even brief contact with cold water can trigger severe pain around the spot. These tumors are small, sometimes only a few millimeters, but the pain they cause is disproportionately large. If you have a painful red spot under one nail that flares in cold temperatures, a glomus tumor is a strong possibility, and surgical removal resolves it.
Cherry-Red Nails From Carbon Monoxide
Bright cherry-red nail beds can be a sign of carbon monoxide poisoning. Carbon monoxide binds to hemoglobin roughly 200 times more tightly than oxygen does, forming a compound that gives blood an unusually vivid red color. This shows through the nail beds and skin. Carbon monoxide poisoning is a medical emergency. If your nails and skin look abnormally bright red and you’re experiencing headache, dizziness, confusion, or nausea, especially in an enclosed space with a fuel-burning appliance, get into fresh air immediately and call emergency services. Cyanide poisoning can produce a similar cherry-red appearance.
What the Pattern Tells You
The number of nails involved and the exact location of the redness are the two most useful clues. A single nail with redness after an injury is rarely a concern. A single nail with a persistent red streak or painful red spot needs professional evaluation to rule out tumors. Multiple nails showing the same change at the same time, whether it’s splinter hemorrhages, red lunulas, or a half-and-half color pattern, often points to a systemic condition affecting your heart, kidneys, liver, or immune system.
Redness that comes with pain, swelling, pus, or fever suggests infection. Redness that appears gradually across many nails without pain tends to reflect something happening internally. If you have diabetes, a weakened immune system, or poor circulation, even mild nail infections warrant prompt attention since your body may struggle to fight them off on its own.