Why do I have red lines under my nails and what do they mean?

Red lines under the nails, often called splinter hemorrhages, are thin streaks of blood that appear beneath the nail bed. Their color, pattern, and location can offer important clues about the underlying cause.

Common causes of red lines under nails include:

• Nail trauma or injury – the most frequent cause, usually harmless
• Endocarditis – a serious infection of the heart's inner lining
• Psoriasis or eczema – skin conditions that affect the nails
• Vasculitis or lupus – autoimmune conditions causing inflammation
• Fungal nail infections – can cause discoloration and streaking
• Certain medications – such as blood thinners

When to be concerned: Multiple red lines across several nails, especially without recent injury, may signal a systemic condition that needs medical attention.

Because red lines under your nails can range from a minor bruise to a warning sign of something more serious like heart or autoimmune disease, guessing isn't the safest option. Take a free, instant, online symptom check to better understand what may be causing your symptoms and get personalized guidance on your next steps.

Reviewed for medical accuracy: 07/15/2026