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Published on: 8/20/2026
What are the potential causes of horizontal red lines under my fingernails?
Horizontal red lines under the fingernails, often called splinter hemorrhages, appear as thin reddish-brown streaks beneath the nail. They can result from minor nail trauma, but they may also signal underlying medical conditions such as endocarditis (a heart infection), psoriasis, vasculitis, or nutritional deficiencies. Because the causes range from harmless to serious, medical evaluation is often recommended—especially if the lines appear on multiple nails, occur without injury, or are accompanied by other symptoms like fever, fatigue, or joint pain.
Identifying the cause early can make a meaningful difference in treatment and outcomes. Rather than guessing or waiting, the smartest next step is to gather clear information about your symptoms. A free, instant, online symptom check can help you understand possible causes, assess urgency, and guide you toward the right type of care—all in just a few minutes.
Reviewed for medical accuracy: 07/15/2026
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Explanation
Horizontal red lines under the fingernails, also known as nail bands, can have several potential causes. According to the provided references, these lines could be related to specific nail conditions or systemic health issues. However, the exact cause can vary, and sometimes these lines appear in individuals without any underlying health problems.
Possible Causes:
- Nail Conditions: Sometimes, horizontal lines or bands may be due to changes in the nail itself. This can include trauma or pressure on the nail.
- Systemic Conditions: In some cases, these lines might be associated with broader health issues. For example, they could be linked to changes in the body that affect nail growth.
It's important to note that while these references provide insights into potential causes, they do not cover every possible reason for horizontal red lines under the nails. If you notice such changes in your nails, you can use Ubie's free AI-powered symptom checker to get personalized insights about your symptoms and determine whether you should seek medical evaluation for appropriate care.
(References)
Chang C, Beutler BD, & Cohen PR. (2017). Report of a Patient with Multiple Horizontal Red Bands .... Dermatology and therapy, 28260214.
Oanță A, Iliescu V, & Țărean S. (2017). Half and Half Nails in a Healthy Person. Acta dermatovenerologica Croatica : ADC, 30064606.
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