A subungual hematoma is a collection of blood that pools between the nail bed and the hard nail plate, typically occurring after blunt trauma like a crush injury. This pooling blood causes intense, throbbing pain because the pressure has no immediate way to escape the sealed pocket under the nail. A procedure called trephination, which creates a small hole to drain the blood, can immediately relieve this pressure. However, many people wonder what happens if they let the injury heal naturally. The outcome depends heavily on the size of the hematoma and the extent of the underlying damage.
The Natural Course of Healing Without Intervention
If the hematoma is small and the initial pressure is manageable, the body begins a natural, slow healing process. The liquid blood under the nail clots and dries out, changing its appearance from red or purple to a dark brown or black discoloration. As the blood clots, the acute, throbbing pain caused by pressure usually subsides within a few days.
The dried blood remains fixed to the underside of the nail plate, as the body cannot reabsorb a large clot in this location. The only way for the discoloration to disappear is for the nail to grow out completely. This prolonged process takes several months for a fingernail and potentially up to a year or more for a toenail to fully replace itself.
Potential Risks and Complications of Non-Drainage
Choosing not to drain a large or high-pressure hematoma carries several risks beyond persistent discomfort. If the pooled blood covers a significant portion of the nail, the sustained pressure can damage the delicate tissue underneath, known as the nail bed. This pressure can lead to pressure necrosis, or tissue death, which may increase the likelihood of permanent nail deformation.
The accumulated blood creates a confined, nutrient-rich environment that can provide a medium for bacterial growth if any break in the surrounding skin allows entry. A large, undrained hematoma may also increase the chance of onycholysis, which is the separation of the nail plate from the nail bed, due to the mechanical force of the blood pool. If the underlying trauma was severe, the blood may be concealing an undiagnosed laceration of the nail bed, which requires repair to prevent long-term growth abnormalities.
Long-Term Nail Health and Appearance
The long-term outcome of a subungual hematoma centers on the appearance and structural integrity of the nail as it regrows. The temporary discoloration persists until the entire nail is replaced, serving as a visual record of the injury moving forward with nail growth.
In cases where the pressure was high or the underlying trauma was significant, the new nail growing in may exhibit temporary ridging or other structural deformations. A common consequence is the complete or partial shedding of the old nail plate, as the force of the hematoma or the new growing nail pushes the damaged plate off the bed. The nail plate may also become temporarily thicker or more brittle as a result of the injury, a condition known as onychochauxis.
Indicators That Require Immediate Medical Attention
Self-management is only appropriate for minor injuries with tolerable pain and small blood collections. Immediate professional medical evaluation is necessary if the hematoma covers more than 50% of the nail surface, as this volume suggests a higher risk of underlying damage and intense pressure.
A medical professional must also be seen if there is suspicion of an associated severe injury, such as a fracture of the distal phalanx (the fingertip bone). Furthermore, any signs of active infection warrant immediate care, including spreading redness, increased pain, warmth, pus drainage, or a fever. If the pain is severe or worsening despite home care, or if a nail bed laceration is visible through the nail, professional intervention is mandatory to prevent complications.