(See also Overview of Nail Disorders.)
Acute paronychia is a bacterial infection of the cuticle.
In acute paronychia, bacteria (usually Staphylococcus aureus or streptococci) enter through a break in the skin resulting from a hangnail, trauma to a nail fold (the fold of hard skin at the sides of the nail plate where the nail and skin meet), loss of the cuticle (the skin at the base of the nail), or chronic irritation (such as that caused by water and detergents). Acute paronychia on the fingers is more common among people who bite or suck their fingers. In toes, infection often begins at an ingrown toenail. Some new drugs used to treat certain cancers or suppress the immune system (for example, after an organ transplant) also seem to sometimes cause acute paronychia. These drugs include gefitinib, erlotinib, sirolimus, everolimus, vemurafenib, dabrafenib, and related drugs.
Acute paronychia develops along the nail margin (the sides and base of the nail fold). Over the course of hours to days, people with acute paronychia develop pain, warmth, redness, and swelling. Pus usually accumulates under the skin along the nail margin and sometimes beneath the nail. Rarely, infection penetrates deep into the finger or toe and can threaten the digit or, in extreme cases, the arm or leg. These deeper infections mainly occur in people who have diabetes or other disorders that cause poor circulation.
The doctor makes the diagnosis by examining the affected finger or toe. In its earliest stage, acute paronychia may be treated with an antibiotic taken by mouth (such as dicloxacillin, cephalexin, or clindamycin) and frequent warm soaks to increase the blood flow. If pus accumulates, it must be drained. The doctor numbs the finger or toe with a local anesthetic (such as lidocaine) and lifts up the nail fold with an instrument. Cutting the skin is usually unnecessary. A thin gauze wick can be inserted for 24 to 48 hours to allow the area to drain.