Discovering a toenail that has turned black and is beginning to detach can be concerning. This condition is common and often results from manageable issues. The black color signals a change in the tissue underneath the nail plate, and detachment is the body’s natural process for shedding a damaged structure. Understanding the underlying cause helps determine the appropriate path forward.
Identifying the Cause of the Black Color
The most frequent reason for a toenail to turn black is a subungual hematoma, which is a bruise underneath the nail plate. This occurs when blood vessels in the nail bed rupture, causing blood to pool between the nail and the underlying tissue. Acute trauma, such as dropping a heavy object on the toe, leads to immediate dark discoloration often accompanied by throbbing pain and pressure.
The discoloration can also result from chronic micro-trauma, common in runners or those wearing ill-fitting shoes. Repetitive impact causes small, continuous injuries that lead to a slow accumulation of dried blood, which appears dark brown or black over time. This form of injury may develop without a single noticeable painful event.
A fungal infection, known as onychomycosis, is the second common reason for dark discoloration. Certain fungi cause the accumulation of dark, crumbly debris underneath the nail, or the infection itself can turn the nail brown, yellow-black, or gray. Unlike a hematoma, fungal discoloration develops slowly and is often accompanied by thickening and brittleness of the nail.
In rare instances, a persistent dark streak or spot appearing without trauma can signal subungual melanoma, a serious form of skin cancer. This discoloration often presents as a dark band starting at the cuticle and growing outward. If the pigment spreads from the nail plate onto the surrounding skin (Hutchinson’s sign), it requires immediate medical evaluation.
Why the Toenail is Separating
The process of the toenail separating from the underlying skin is called onycholysis. This detachment results from injury or disease affecting the connection between the nail plate and the nail bed. The separated portion of the nail cannot reattach itself, so the focus shifts to protecting the nail bed until a new, healthy nail grows in.
In the case of a subungual hematoma, the pooled blood creates intense pressure that physically forces the nail plate away from the nail bed. Once this bond is broken, the nail naturally lifts and eventually sheds as the new nail pushes the old one off. This shedding process can take several weeks or months following the initial trauma.
When separation is caused by a fungal infection, the organisms degrade the keratin forming the nail plate and supporting tissue. This degradation compromises the structural integrity of the attachment, causing the nail to lift, often starting at the free edge. The resulting gap creates an environment where the infection can worsen and cause further detachment.
Toenails grow slowly, averaging about 1 millimeter per month. Complete regrowth of a large toenail can take up to 18 months. During this period, the separated nail acts as a protective shield for the sensitive nail bed underneath until it is fully pushed off by the new growth.
Immediate Next Steps and Medical Consultation
Home Care for a Separating Nail
If the toenail is separating, protect the exposed nail bed and keep the area clean. Trim the detached portion back to where it is still attached to prevent further trauma. Cleanse the toe gently with mild soap and water daily, and cover the area with a clean, dry bandage to shield the sensitive tissue.
Wear comfortable, well-fitting footwear that does not put pressure on the affected toe. Avoid attempting to forcibly remove the entire nail, as the remaining portion provides a barrier against infection. Allowing the nail to shed naturally as the new nail grows underneath is the safest approach.
When to Seek Medical Attention
Medical consultation is recommended if the black discoloration appeared without any known injury, requiring diagnosis to rule out serious conditions like melanoma. Seek immediate care if you experience signs of a bacterial infection, including increasing pain, noticeable swelling, warmth, or the presence of pus around the nail.
A doctor can relieve pressure from a large, painful subungual hematoma by creating a small hole in the nail plate to drain the trapped blood (trephination). If a fungal infection is suspected, a medical professional can confirm the diagnosis and prescribe appropriate antifungal treatment, as these infections rarely resolve without medication.