A purple discoloration under a toenail often indicates an underlying issue, ranging from minor incidents to conditions that warrant medical attention. Understanding the various reasons behind a purple toenail is important for determining if professional evaluation is necessary.
Common Causes: Injury
The most frequent cause of a purple toenail is trauma, leading to a condition known as a subungual hematoma. This occurs when blood vessels beneath the nail plate rupture, causing blood to pool in the space between the nail and the nail bed. Common incidents include stubbing a toe forcefully, dropping a heavy object directly onto the nail, or experiencing repetitive microtrauma.
Wearing shoes that are too tight, especially in the toe box, can also contribute to this condition by applying constant pressure during walking or running. Athletes, particularly long-distance runners, frequently develop subungual hematomas from repeated toe impact against their shoes. The trapped blood typically appears as a dark red, blue, or purple spot that can spread to cover the entire nail.
The discoloration emerges shortly after injury and may cause throbbing pain due to pressure buildup under the nail. As the nail grows, the discolored area will gradually move forward and grow out. This process can take several months, depending on individual nail growth rate.
Other Potential Underlying Reasons
While injury is common, other factors can also lead to a purple toenail. Severe or long-standing fungal infections (onychomycosis) can cause the nail to appear discolored, including shades of dark brown, black, or purplish hues. This discoloration can result from debris accumulating under the nail or from secondary bacterial infections that alter the nail’s appearance.
Bacterial infections, especially those spreading beneath the nail plate, can also cause discoloration. While often accompanied by swelling, redness, warmth, or pus, a severe bacterial infection can contribute to a darker appearance. These infections require prompt medical evaluation to prevent complications.
Certain medications can induce nail discoloration as a side effect. Some chemotherapy drugs, antimalarial medications, and certain antibiotics can cause bluish or purplish nail discoloration. This discoloration affects multiple nails and resolves after the medication is discontinued.
Rarely, systemic health conditions can impact nail bed color. Conditions affecting circulation, such as Raynaud’s phenomenon, can cause temporary bluish discoloration due to reduced blood flow. Certain vascular disorders can also influence nail bed appearance.
A rare but serious cause of dark nail discoloration is subungual melanoma, a form of skin cancer. This condition often presents as a dark streak or patch under the nail, appearing black, brown, or purplish. Unlike a bruise, melanoma does not grow out with the nail and may have irregular borders or spread to the surrounding skin of the cuticle or nail fold. Monitor any dark streaks under the nail that do not resolve or change over time.
When to Seek Professional Help
Recognizing when a purple toenail requires medical attention is important. Seek professional help if the discoloration is accompanied by severe or increasing pain, particularly if throbbing and persistent. Signs of infection, such as redness, swelling, warmth, or pus around the nail, also warrant medical evaluation.
If the discoloration does not improve or grow out with the nail over several months, or if it appears to be spreading to the surrounding skin, consult a doctor. This is especially true for irregular or spreading dark streaks, which could indicate subungual melanoma. A medical professional should also assess any purple toenail if the cause is unknown or if you have underlying health conditions. Individuals with diabetes, compromised immune systems, or circulation problems should seek prompt medical advice for any nail changes.
Diagnosis, Treatment, and Prevention
Diagnosing the cause of a purple toenail begins with a physical examination by a doctor or podiatrist. They will assess the nail, review your medical history, and inquire about any recent injuries or symptoms. In cases of suspected fungal infection, a nail clipping or scraping may be taken for laboratory analysis to identify the fungus.
If subungual melanoma is a concern, a biopsy of the nail matrix or nail bed will be performed to examine the tissue for cancerous cells. For large or painful subungual hematomas, treatment may involve trephination, where a small hole is made in the nail plate to drain trapped blood and relieve pressure. Fungal infections are treated with oral antifungal medications or topical solutions, while bacterial infections require antibiotics.
Minor injuries only need monitoring as the nail grows out. Preventing purple toenails involves protecting your feet. Wearing properly fitting shoes that provide adequate toe room and cushioning is important, especially during physical activity. Protecting your feet with appropriate footwear when engaging in activities that could cause injury, such as moving heavy objects, can also prevent trauma. Regular nail care, including keeping nails trimmed to a proper length, can minimize the risk of injury.