Purple nails, medically known as chromonychia, are a noticeable change in the color of the nail bed that often signals an underlying issue. This discoloration can range from a bluish tint to a deep purple or black hue. The color change is typically related to the status of the blood circulating beneath the nail or a localized physical event.
How Nail Color Reflects Blood Status
The color visible through the translucent nail plate is determined by the oxygen saturation of the blood flowing in the capillaries of the nail bed. Oxygenated blood, which is rich in oxygen, appears bright red due to hemoglobin. When blood is deoxygenated, hemoglobin changes structure, causing the blood to appear bluish or purplish. This purplish discoloration resulting from low oxygen is called cyanosis.
Cyanosis can be generalized, affecting the entire body, or peripheral, confined to the extremities like the fingers and toes. Peripheral cyanosis occurs when slowed blood flow allows tissues to extract more oxygen than usual, leaving behind deoxygenated blood. A quick circulation check involves observing the color return after pressing the nail; a delayed return to pink suggests poor blood oxygenation or circulation.
Localized Causes of Purple Nails
Many cases of purple nails are caused by localized trauma or temporary circulatory changes rather than systemic disease. The most common localized cause is a subungual hematoma, which is a bruise underneath the nail plate. This occurs when a direct injury, such as slamming a finger or dropping an object, ruptures small blood vessels beneath the nail. The blood pools between the nail bed and the nail plate, causing a dark red, purple, or black discoloration that remains until the nail grows out.
Repetitive microtrauma, such as from ill-fitting shoes, can also cause a subungual hematoma. Exposure to extreme cold is another temporary, non-systemic cause, as it constricts blood vessels, reducing local blood flow and causing reversible peripheral cyanosis.
Underlying Systemic Health Issues
When purple nails are not caused by trauma or cold, they may signal systemic health conditions that impair oxygen delivery or circulation. These issues lead to a persistent form of cyanosis.
Respiratory and Cardiovascular Causes
Respiratory illnesses prevent sufficient oxygen from entering the bloodstream, causing a drop in arterial oxygen saturation. Examples include severe pneumonia, chronic obstructive pulmonary disease (COPD) exacerbations, or acute respiratory distress syndrome (ARDS). Cardiovascular problems also manifest as purple nails because the heart is unable to pump blood effectively to the extremities. Conditions like heart failure or certain congenital heart defects result in poor blood flow, leading to increased oxygen extraction and peripheral cyanosis.
Vascular and Blood Disorders
Certain vascular disorders, such as Raynaud’s phenomenon, involve temporary, intense spasms of the small blood vessels in the fingers and toes, which severely restricts blood flow and turns the nails blue or purple. Other systemic conditions affect the blood’s ability to carry oxygen. Methemoglobinemia, a rare disorder, involves an abnormal form of hemoglobin that cannot effectively release oxygen to the tissues, leading to a slate-blue hue in the nail beds. The purple color results from a chemical change in the blood itself, not poor circulation. Systemic cyanosis, involving both the extremities and mucous membranes, suggests a significant problem with the lungs or heart’s ability to oxygenate blood.
Identifying Urgent Symptoms
Differentiating between a benign cause like a bruise and a serious internal problem requires attention to accompanying symptoms. If the purple discoloration is isolated to one nail and follows a known injury, it is likely a subungual hematoma and not a medical emergency. However, if the purple color appears suddenly and affects multiple nails, immediate medical attention is necessary.
Urgent warning signs include shortness of breath, difficulty breathing, or gasping for air, which indicate severe oxygen deprivation. Other serious symptoms are chest pain, dizziness, fainting, or sudden confusion. These combinations can signal a life-threatening event like a pulmonary embolism, heart attack, or acute respiratory failure. If the discoloration spreads rapidly or does not return to a normal pink color after warming or massaging, seek professional evaluation quickly.