Nail discoloration is a common issue with various underlying factors, from minor injuries to significant health conditions. This article explores the reasons nails might darken, their causes, and how to address them.
Reasons for Dark Nails
Physical trauma is a common cause of dark nails, resulting in a subungual hematoma (bleeding under the nail). This occurs from injuries like stubbing a toe or hitting a finger, causing blood vessels beneath the nail plate to break and blood to collect. The discoloration initially appears red or purple, turning brown or black as blood clots and dries. The pressure from this pooled blood can lead to pain and throbbing.
Fungal infections (onychomycosis) are a frequent reason for nail discoloration. They can cause the nail to appear white, yellow, brown, green, or black. The nail may also thicken, become brittle, or separate from the nail bed. Common culprits include dermatophytes, yeasts, and molds.
Bacterial infections can also cause dark nail changes. For instance, Pseudomonas aeruginosa can cause a distinctive green-black nail discoloration. This occurs when bacteria produce pigments incorporated into the nail plate.
Certain medications can cause nail darkening as a side effect. Some antibiotics, chemotherapy drugs, and antimalarial drugs cause blackish-brown discoloration. This pigmentation often arises from changes in melanin production or deposition within the nail.
Systemic medical conditions may also cause nail discoloration. Diseases affecting the kidneys or liver, diabetes, and certain autoimmune conditions can be associated with changes in nail appearance. Nutritional deficiencies, such as those involving vitamin B12, vitamin D, or protein, can also result in dark lines on the nails.
Melanin production in the nail matrix can lead to melanonychia, presenting as brown or black pigmentation. This often appears as a longitudinal band. While often benign, especially in individuals with darker skin, a dark streak can sometimes signify subungual melanoma. This serious form of skin cancer appears as a brown or black streak that may widen, change, or be accompanied by nail distortion.
At-Home Approaches
For minor dark nail cases, especially those from superficial stains or mild trauma, certain at-home practices are beneficial. Gentle cleaning with mild soap and water can remove surface dirt and debris. Regularly scrubbing the underside of nails with a brush prevents germ accumulation.
Proper nail care involves keeping nails trimmed short and filed smoothly. This reduces the risk of further trauma and aids in healthy nail plate growth. Moisturizing nails and cuticles also supports overall nail health and flexibility.
Over-the-counter (OTC) solutions like antifungal creams or ointments (e.g., terbinafine or clotrimazole) are available. These may benefit mild fungal infections, particularly if superficial. However, these topical treatments are often less effective for deep or widespread infections as they may not penetrate the nail adequately. Avoid harsh chemicals or home bleaching agents, as these can damage the nail plate and surrounding skin.
When to Consult a Doctor
Consult a doctor when dark nail discoloration appears without a clear cause, such as a recent injury. If the darkness spreads, changes rapidly in size or color, or affects only one nail, it warrants evaluation. A brown or black streak that increases in size or does not heal should be examined.
Accompanying symptoms like pain, swelling, pus, or a foul odor around the nail also indicate a doctor’s visit. These signs suggest an infection or other underlying issue requiring medical attention. If home remedies show no improvement, or if nail discoloration accompanies other systemic symptoms, professional consultation is important. Any suspicion of subungual melanoma, such as a new or changing dark streak, necessitates prompt medical assessment.
Professional Medical Interventions
When consulting a doctor for dark nails, diagnosis typically begins with a physical examination. To identify fungal infections, a nail clipping may be taken for microscopic examination and culture. If subungual melanoma is suspected, a nail unit biopsy may be performed to analyze cells for cancerous changes.
Treatment options vary by diagnosis. For fungal infections, oral antifungal medications like terbinafine are often prescribed, offering higher effectiveness than topical solutions. Topical antifungal polishes or creams are also available for milder cases. Bacterial infections are managed with antibiotics.
For subungual hematomas causing significant pain, trephination may be performed. This involves creating a small hole in the nail plate to drain blood and relieve pressure. If a systemic condition is the root cause, treating that disease can often resolve the nail discoloration. For confirmed subungual melanoma, surgical removal of the affected nail and surrounding tissue is the primary treatment.
Keeping Nails Healthy
Maintaining nail health can prevent various forms of discoloration. Practicing good foot and hand hygiene, including regular washing and thorough drying, deters infections. Keeping nails clean and dry prevents bacteria and fungi from thriving underneath them.
Wearing well-fitting shoes and breathable materials prevents trauma and reduces toenail issues. Protecting nails from physical impact or harsh chemicals by wearing gloves during chores is also beneficial. A balanced diet rich in protein, biotin, iron, and zinc supports nail strength and growth. Regularly inspecting nails for changes allows for early detection of concerns.