How to Treat an Infected Nail (Paronychia)

Infection around a man's thumb nail

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The hand is a wonderful instrument wherein form and function are intricately related. With such detailed anatomy, there are plenty of compartments, spaces, and folds where bacteria can hide and fester.

Although you may be unfamiliar with the term, you might have experienced a paronychia in the past. Paronychia is a nail infection that affects the lateral nail fold and perionychium. In other words, a paronychia is an infection of the soft tissue bordering the nail itself and usually affects either the vertical portions of the nail or the horizontal portion of the nail.


You can get a paronychia secondary to a minor injury like biting your nails, pulling a hangnail, biting a hangnail, or pushing the cuticles back during a manicure — any type of trauma that introduces bacteria into the fleshy part of your finger.

It may come as a surprise that the dirtiest bites originate from the human mouth; thus, bacteria isolated from paronychia often include all types of bacteria, both aerobic and anaerobic. Chief among these bugs are species of staph and strep (Staphylococcus Aureus and Streptococcus species).

Dishwashers or housekeepers can develop chronic, or recurring, paronychia secondary to exposure to cleaning solutions and moisture. Typically, such paronychia are due to a fungus called Candida albicans.

The diagnosis of paronychia is based on physical exam and cultures aren't usually needed. Sometimes an x-ray may be useful to look for a foreign body or evidence of bone infection (i.e., osteomyelitis).

Paronychia are exquisitely painful and occur infrequently in most healthy people. However, some immunocompromised people (think people with AIDS) experience chronic paronychia. Furthermore, people with diabetes or fungal nail infections can get paronychia caused by fungus (which is treated with antifungal medication).

Signs and Symptoms

Most paronychia begin with a few days of pain, tenderness, and swelling of the finger followed by pus collecting at the surface of the infection. This pus becomes fluctuant and comes to a head. This head is a natural point of drainage.

Until a head forms, or pus becomes otherwise identifiable at the level of trauma, a physician (or other healthcare provider) won't be able to incise the paronychia and drain the pus. Instead, antibiotics, elevation of the hand, and warm compresses are prescribed. Antibiotics are definitely needed if the skin infection is extensive (i.e., extensive cellulitis) or lymph vessels become infected (a process called lymphangitis).


The antibiotics most commonly used to treat paronychia are TMP/SMX (Bactrim) and a cephalosporin named cephalexin (Keflex). In case infection with anaerobic bacteria is suspected, clindamycin (Evoclin) or amoxicillin-clavulanate (Augmentin) is given with Bactrim. Of note, Bactrim is effective against drug-resistant bacteria. 

To release a paronychia, a physician can elevate the hardened bit of skin immediately bordering the nail itself (eponychium) using a blade so as to open up a route of drainage for the pus. Alternatively, a physician can directly slice into the fluctuant portion of the infection; this procedure is no different from draining any other type of abscess or boil.

Because paronychia are pretty superficial, a digital nerve block (anesthesia) is unnecessary to drain most infections of pus. In fact, anesthetizing the area will likely result in added pain with little benefit. Rest assured that the actual pain of draining a paronychia pales in comparison to either the pain of the condition or the relief felt after the pus is drained.

Sometimes paronychia can extend under part of the nail. In these cases, either part or all the nail needs to be removed. A paronychia that is left untreated can sometimes surround the entire nail margin and result in a "floating" nail.

After a paronychia is drained of pus, there is usually no need for antibiotics. However, if the paronychia is accompanied by localized cellulitis or skin infection, then antibiotics are needed to treat the skin infection.

Ultimately, a paronychia must be drained of pus before you experience relief. It may take a paronychia several days be able to be drained of pus — the process isn't immediate. If you see a physician before the paronychia has "ripened" and pus is visible at the surface of the infection, the area can't be drained, and you'll leave the office with a prescription for antibiotics and instructions to soak the area until the infection is ripe for drainage of pus.

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Article Sources

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  • Ewen B, Hart RG. Chapter 29. Hand Trauma. In: Stone C, Humphries RL. eds. CURRENT Diagnosis & Treatment Emergency Medicine, 7e New York, NY: McGraw-Hill; 2011.
  • Germann CA, Fourre MW. Chapter 280. Nontraumatic Disorders of the Hand. In: Tintinalli JE, Stapczynski J, Ma O, Cline DM, Cydulka RK, Meckler GD, T. eds. Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7e. New York, NY: McGraw-Hill; 2011.