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What is a blister under the big toenail?

Published in Toenail Health 4 mins read

What is commonly referred to as a "blister under the big toenail" is most often a subungual hematoma, a condition where blood and other fluids collect underneath the toenail. This collection creates pressure and discoloration, appearing much like a dark-colored blister.

Understanding a Subungual Hematoma

A subungual hematoma is a transient (temporary) condition characterized by the accumulation of blood and fluid beneath the nail plate. While a typical blister forms between layers of skin and contains clear or yellowish fluid, a subungual hematoma specifically involves blood pooling under the hard nail plate. This is distinct from a skin blister, though the visible swelling and fluid-filled appearance lead to the common comparison.

Common Causes

The primary cause of a subungual hematoma is traumatic injury to the toe or nail. This trauma causes small blood vessels under the nail to rupture, leading to bleeding into the confined space.

Common scenarios include:

  • Impact Injuries:
    • Stubbing your toe forcefully against a hard object.
    • Dropping a heavy object directly onto your big toenail.
    • Hitting your toe with a hammer or similar tool.
  • Repetitive Microtrauma:
    • Wearing shoes that are too tight, especially in the toe box, during prolonged activities like running or hiking.
    • Activities involving frequent stopping, starting, or downhill running, where the toes repeatedly hit the front of the shoe.
    • Wearing shoes that are too loose, allowing the foot to slide forward and backward, causing friction and impact.
  • Nail Clipping Accidents: Improper or aggressive nail trimming that causes injury to the nail bed.

Symptoms and Appearance

A subungual hematoma under the big toenail typically presents with several characteristic signs:

  • Pain: Often immediate and throbbing, due to the pressure of blood accumulating under the nail.
  • Discoloration: The nail may appear black, purple, dark red, or brown. The color can change over time as the blood clots and breaks down.
  • Pressure: A sensation of pressure under the nail, which can intensify the pain.
  • Visible Swelling: Though the nail plate prevents outward swelling, the accumulation of fluid can visibly raise the nail slightly in severe cases.
Symptom Description
Pain Throbbing, aching sensation due to pressure build-up.
Discoloration Nail turns black, blue, purple, or dark red from pooled blood.
Pressure Sensation Feeling of tightness or fullness under the nail.
Nail Detachment In severe cases, the nail may lift or eventually fall off.
Tenderness Pain upon touching or putting weight on the affected toe.

Treatment and Recovery

For minor subungual hematomas, treatment often involves self-care and waiting for the nail to grow out. The discolored area will gradually move forward with nail growth and eventually be trimmed away. However, for larger or more painful hematomas, medical intervention may be necessary.

Home Care (for minor cases):

  • RICE Method:
    • Rest: Limit activity to avoid further trauma.
    • Ice: Apply an ice pack wrapped in a cloth for 15-20 minutes several times a day to reduce swelling and pain.
    • Compression: Gently bandage the toe if it helps with comfort.
    • Elevation: Keep the foot elevated to reduce blood flow to the area.
  • Pain Relief: Over-the-counter pain relievers like ibuprofen or acetaminophen can help manage discomfort.

Medical Intervention (for severe cases):

If the pain is severe or the hematoma covers a significant portion of the nail, a doctor may perform a procedure called trephination. This involves:

  1. Creating a small hole: A sterile needle, heated paperclip, or medical cautery device is used to create a tiny hole in the nail plate.
  2. Draining the blood: This hole allows the trapped blood and fluid to drain, immediately relieving pressure and pain.
  3. Cleaning: The area is cleaned and dressed to prevent infection.

This procedure should only be performed by a healthcare professional due to the risk of infection or further injury.

Prevention

Preventing subungual hematomas largely involves protecting your feet and wearing appropriate footwear:

  • Proper Footwear:
    • Ensure your shoes fit well, providing enough room in the toe box without being too loose. There should be about a thumb's width of space between your longest toe and the end of your shoe.
    • Wear appropriate shoes for specific activities, such as running shoes for athletic pursuits or steel-toed boots for work in hazardous environments.
  • Protect Your Feet:
    • Be mindful of your surroundings to avoid stubbing your toes.
    • Wear protective footwear when performing tasks that could result in objects falling on your feet.
  • Nail Care:
    • Keep toenails trimmed to a moderate length, not too long or too short, to prevent them from hitting the inside of your shoes.
    • Trim nails straight across to avoid ingrown toenails, which can also cause pain and discomfort.

By understanding the causes and taking preventative measures, you can significantly reduce the risk of developing a subungual hematoma under your big toenail.