An infection inside the tip of the finger can form an enclosed pocket of pus (or abscess) that is very painful as it expands. A felon is a fingertip abscess deep in the palm side of the finger. It usually is caused by bacterial infection, but a herpes virus called herpetic whitlow and, more rarely, fungi also can cause felons.
Felons usually are caused by Staphylococcus aureus bacteria. It is important to get treatment quickly for these small abscesses. If the bacteria pocket continues to expand, it can compress blood vessels in the finger and cut off the fingertip's circulation, causing in permanent damage to the finger. Also, an untreated felon can spread its infection to the bone within the finger. This can lead to a more serious infection, called osteomyelitis, which takes much longer to cure.
Like other types of infections, felons sometimes begin after the finger is punctured by a wood splinter or something else.
A felon causes extreme pain at the fingertip, especially when pressure is applied to the "fingerprint" surface. The end of the finger swells, is warm and turns red. There may be an accumulation of a white, thick discharge (pus). As the felon increases, the fingertip may feel numb, and bending the finger may be painful.
Your doctor can usually diagnose a felon just by examining it. He or she will ask whether you have had an injury in the area. Tenderness, redness, firmness and enlargement of the fingertip are all signs of a felon. If you have small bubble-like cysts on the skin, called vesicles, and repeated episodes, it is likely the cause is herpetic whitlow.
Because an enlarging abscess in the finger reduces blood supply into the area, it is hard for your body's immune system to fight this type of infection. Felons almost always need to be opened and drained by a doctor before they can heal. Most clear up within days to weeks. Healing may be faster with aggressive treatment.
If you are going to work with wood or other materials that could cause splinters, wear protective gloves. People with diabetes who prick their fingers for home blood tests should first wash the fingertip with alcohol. Avoiding contact with others who have herpes may prevent herpetic infections, though there may be no way to know in advance who has the infection. Prompt diagnosis and treatment of a herpetic infection may prevent complications.
Except for infections related to herpes, felons are treated with a minor surgery to allow drainage. Typically, your doctor will make the whole finger numb by injecting an anesthetic once into each side of your finger, just beyond the knuckle of the hand. Then he or she will make one or more small cuts in the tip of your finger to allow the pus to drain out. A narrow gauze strip may be left in the wound to hold it open for continued drainage. The gauze may need to be replaced every day or two as it absorbs bacteria and debris from inside the wound.
A doctor usually will prescribe antibiotics that work against "staph" bacteria infections. Antibiotics may be changed if the infection does not clear up promptly or if testing of the pus indicates that the infection is caused by an unusual organism or one that is resistant to the usual antibiotics. For severe cases, a more extensive operation may be necessary including making a small hole in the nail to allow additional drainage.
If the infection is due to herpes, drainage is not done because it may delay healing or increase the risk of bacterial infection. Herpes infections in the finger tend to clear up on their own, although antiviral medication (such as Zovirax) often is prescribed as well.
If you have this or any skin or wound infection, make sure you are up-to-date with your tetanus vaccinations.
Because of the complications that can occur from a felon, you should see your doctor and go to an emergency room for immediate care if you develop sudden or severe pain or swelling in a finger.
The prognosis is excellent. Felons caused by bacterial infections are curable with drainage and antibiotic treatment. Complications are rare and usually can be prevented with prompt diagnosis and treatment.
National Foundation for Infectious Diseases
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Bethesda, MD 20814
Infectious Diseases Society of America
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Alexandria, VA 22314