We often forget about them, but our fingernails can tell us so much about our health. Changes in nail appearance can sometimes be a sign of systemic diseases, vitamin deficiencies, or even just a local infection or injury, such as a nail fungus.
One change you might notice is horizontal red lines running under your fingernails. This article will focus on this specific nail abnormality, technically called longitudinal erythronychia, and describe what causes it, how it’s diagnosed, and when it’s worth seeing a doctor about.
Longitudinal erythronychia shows up as red streaks or bands running from the base of your nail (cuticle) to the tip. Noticing this sign early is key to preventing serious issues, and it can also help you and your doctor tell the difference between a harmless change and one that needs further investigation.
Understanding what causes horizontal red lines under fingernails can help you and your doctor decide on the best course of action, whether it’s just keeping an eye on things or seeking treatment.
Basic nail anatomy and physiology
To understand what those red lines might mean, it’s helpful to know a little about how your nails are structured and how they grow.
Nail structure
Here’s a brief overview of the parts of your fingernails and toenails:
- Nail plate: This is the hard, translucent part of the nail that you can see. It’s made of keratin and protects the sensitive skin underneath.
- Nail bed: This is the skin directly beneath the nail plate. It contains blood vessels and nerves that nourish the nail and allow you to feel sensations.
- Nail matrix: This is the area at the base of the nail where nail cells are produced. If the matrix is damaged, it can cause permanent nail abnormalities.
- Lunula: This is the crescent-shaped white area at the base of the nail.
- Cuticle: This is the skin that overlaps the base of the nail plate, protecting the nail matrix from infection.
Nail growth
Fingernails grow faster than toenails. On average, fingernails grow about 3 millimeters per month, while toenails grow about 1 millimeter per month. Several factors, like age and overall health, can affect nail growth. It takes about 4 to 6 months for a fingernail to completely renew itself.
Distinguishing nail lines: Leukonychia, Melanonychia, and Erythronychia
So, your fingernails have lines. But what kind of lines are they? Here’s a quick guide to some of the different types of nail lines you might see:
- Leukonychia: These are white lines or spots. True leukonychia involves the nail plate itself, while apparent leukonychia is due to changes in the blood vessels under the nail.
- Longitudinal Melanonychia: These are brown or black lines that run from the bottom of your nail to the tip. Melanonychia can be caused by something harmless, but it can also be a sign of melanoma, so it’s important to get it checked out by a doctor.
- Longitudinal Erythronychia: These are red lines that run from the bottom of your nail to the tip. Erythronychia can appear on just one nail or multiple nails. It can be associated with tumors and other underlying health conditions.
Longitudinal Erythronychia: Vertical Red Nail Lines in Detail
Longitudinal erythronychia (LE) means that you have red streaks or bands running from the base of your nail (under the cuticle) to the tip. The streaks appear through the nail, not on the nail.
It’s important to understand that these red lines aren’t horizontal; they’re vertical. If you’re seeing horizontal lines, you may actually be experiencing Beau's lines, which is a different condition.
General Features and Examination
LE can affect just one nail (solitary) or multiple nails. If it’s just one nail, it often means there’s something local going on with that finger or toe. If it’s multiple nails, it’s more likely to be related to a systemic health condition.
When trying to figure out the cause, it’s important to look closely at:
- The number of nails involved.
- How wide the red bands are.
- How intense the red color is.
- Any other symptoms you’re experiencing.
Localized Longitudinal Erythronychia (Single Nail)
If only one nail has these red lines, some possible causes include:
- Glomus Tumor: This is a non-cancerous growth in the glomus body, a specialized structure in your fingertip. It can cause pain, sensitivity to cold, and a bluish-red color under the nail. Usually, surgery is needed to remove it.
- Warts: Warts growing around the nail (periungual warts) can sometimes cause red streaks. Treatment options include freezing them off (cryotherapy), using topical medications, or surgical removal.
- Trauma: A simple injury to the nail base (matrix) can lead to LE. Usually, it will resolve on its own as the nail grows out.
- Other Benign Growths: Non-cancerous growths like fibromas near the nail matrix can also cause these red lines.
Multiple Longitudinal Erythronychia (Several Nails)
When multiple nails are affected, the cause is more likely to be related to a systemic condition:
- Lichen Planus: This is an inflammatory skin condition that can affect the nails, causing thinning, ridges, and red streaks. Treatment often involves topical corticosteroids or other medications that suppress the immune system.
- Darier Disease: This is a genetic skin disorder with characteristic keratotic papules (small, rough bumps) and nail abnormalities, including red and white streaks running lengthwise. It’s linked to mutations in the ATP2A2 gene.
- Psoriasis: While less common, psoriasis can sometimes show up as LE.
- Systemic Lupus Erythematosus (SLE): In rare cases, SLE can cause nail changes, including these red lines.
Other causes of red nail lines: rare conditions and medications
While splinter hemorrhages and injuries are the most common reasons for red lines to appear under your fingernails, some less common conditions can also cause them.
Red streaks associated with systemic diseases
Certain systemic illnesses, like autoimmune disorders, can cause changes in your nails, including red lines. Your doctor will consider your medical history and any other symptoms you’re experiencing to rule out these rare associations.
Medication-induced erythronychia
Sometimes, medications can cause nail changes as a side effect. Chemotherapeutic agents and retinoids are two types of medications that may cause this. If you’re taking medication and notice red lines under your nails, talk to your doctor to see if it could be related.
Inflammatory conditions
Inflammatory conditions like eczema can sometimes affect the nail folds and cause red lines to appear. Other dermatoses can also cause these changes.
Ruling out other nail abnormalities
It’s important to make sure those red lines under your fingernails aren’t something else. There are a few other conditions that can cause lines or marks on your nails, and it’s important to know the difference.
- Splinter hemorrhages: These are tiny, dark red lines that run vertically under the nail. You’ll often see them after an injury to the nail. Splinter hemorrhages are shorter and more irregular than the horizontal red lines we’re discussing, and they don’t run the full length of the nail. Sometimes, splinter hemorrhages are a sign of endocarditis, so be sure to consult with your doctor.
- Longitudinal melanonychia: These present as brown or black lines. The color is the biggest difference here. If you see brown or black lines, you should rule out the possibility of subungual melanoma with your doctor.
- Leukonychia: These are white lines, not red. There are two types: true and apparent.
When to suspect malignancy and refer
While horizontal red lines under your fingernails, or longitudinal erythronychia, are usually harmless, there are a few times when they could point to something more serious. Here’s when it’s time to get a professional opinion:
- Changes in the nail: If the red band changes suddenly in color, width, or shape, that’s a red flag.
- Nail dystrophy: Is the nail plate distorted or destroyed? That’s another reason to worry.
- Lack of response to treatment: If the red line sticks around despite treating any underlying conditions, it’s worth getting checked out.
Although dark vertical lines (melanonychia) are more associated with melanoma, any weird nail change deserves a closer look, especially if:
- You or a family member has a history of melanoma.
- You’ve spent a lot of time exposed to UV radiation.
If any of these apply to you, get yourself to a dermatologist. They’re the experts in diagnosing and treating nail disorders. They might even recommend a biopsy to rule out anything nasty. Catching nail melanoma early can dramatically improve your chances of a good outcome, so don’t delay!
Frequently Asked Questions
What are the signs of heart disease in fingernails?
While horizontal red lines (splinter hemorrhages) can sometimes be linked to heart issues like endocarditis, they are more often caused by minor trauma. Other nail changes suggestive of heart disease might include clubbing (enlargement of the fingertips and thickening of the nails) or bluish discoloration (cyanosis).
What does a red line under your fingernail mean?
A single red line, also known as a splinter hemorrhage, usually indicates damage to the small blood vessels under the nail. This is most commonly due to minor injuries to the nail bed, but in rare cases, it can signal a more serious underlying condition, such as an infection or systemic disease.
What autoimmune disease causes lines in fingernails?
Several autoimmune diseases can affect the nails. Psoriasis, for example, can cause pitting, thickening, and separation of the nail from the nail bed. Lupus might cause nail changes like redness, swelling around the nail fold, and splinter hemorrhages.
What do RA fingernails look like?
Rheumatoid arthritis (RA) itself doesn’t directly cause specific nail changes, but medications used to treat RA can have side effects on the nails. Additionally, some people with RA may develop nailfold inflammation (paronychia), leading to redness and swelling around the nail.
What do fingernails look like with low iron?
Low iron, or iron deficiency anemia, can sometimes cause changes in the nails. One common sign is koilonychia, also known as spoon nails, where the nails become thin and concave, resembling a spoon. Brittle nails are another possible symptom.
Closing Thoughts
Horizontal red lines under your fingernails, also known as longitudinal erythronychia, can point to different underlying health issues, from harmless tumors to systemic diseases. It’s important to carefully examine your nails and make sure the lines aren’t caused by something else.
If you notice changes in your nails that you can’t explain, especially if you have other symptoms or risk factors, see a doctor. Getting a diagnosis and starting treatment early can help you avoid complications and improve your health.
Scientists need to do more research to understand what causes longitudinal erythronychia and how to treat it. They need to develop non-invasive ways to diagnose it and find new targets for treatment.
Nail problems, like nail fungus, can be worrying, but knowing what might be causing them and getting medical care when you need it can help you stay healthy and feel your best.