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The most common pathogens causing hand infection are Staphylococcus aureus, Streptococcus species, and gram-negative species.1 Polymicrobial infections are common, especially with inoculation of mouth flora. In most U.S. cities, community-associated methicillin-resistant Staphylococcus aureus is the most common pathogen cultured from patients with skin and soft tissue infections in EDs,2 including 47% to 78% of hand infections.3,4,5,6,7,8

Injection drug users typically present with abscesses or deep space infections secondary to S. aureus and gram-negative organisms.9 These infections are most commonly caused by direct introduction, but hematogenous spread from bacterial endocarditis is a possibility (see chapter 296, "Injection Drug Users").

Hand infections are also discussed in chapter 46, "Puncture Wounds and Bites."

Paronychia and felons are caused by minor trauma like chewing fingernails or exposing minor injuries to saliva. Most of these infections are polymicrobial including anaerobic bacteria.

Infections caused by animal bites reflect the oral flora of the involved species. Bites introduce a broad range of bacteria, including gram-positive, anaerobic, and gram-negative organisms. Common pathogens include streptococci, staphylococci, Haemophilus, Eikenella, Fusobacterium, peptostreptococci, Prevotella, and Porphyromonas species.10 Cat and dog bites harbor Pasteurella multocida, which typically produces an aggressive, rapidly spreading cellulitis that becomes suppurative. (See chapter 46.)

Patients with diabetes or acquired immunodeficiency syndrome have common bacterial infection or develop atypical infections, including those caused by Mycobacterium or Candida albicans. Those who are immunocompromised or asplenic are at risk for rapid progression and require prompt source control and antibiotics.


Hand infections are most commonly introduced by an injury to the dermis. The infection initially may remain superficial and broader, termed cellulitis, or be localized as seen in a paronychia or felon. Left untreated, infections may spread along anatomic planes or to adjacent compartments in the hand. Deeper injuries may directly seed underlying structures, creating rapidly spreading infections such as those seen with closed fist injuries or cat bites.

Obtain a directed history to delineate a likely cause of the infection. The physical examination should note the anatomic limits of the infection. Look for skin, subcutaneous tissue, fascial space, tendon, joint, or bone involvement. If deep structures of the hand are involved, emergently consult a hand specialist because treatment likely will involve inpatient care and operative drainage.

With the exception of superficial cellulitis, hand infections are managed using basic principles. First, incise and drain any collection of pus. Superficial and discrete infections, such as paronychia and felons, can be drained in the ED. Deep infections are better treated in the operating room by a hand surgeon. Second, immobilize and elevate the extremity. This will rest ...

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