Human Bite Infections

Human Bite Infections



Human bite infections are potentially serious infections caused by rapid growth of bacteria in broken skin.


Bites—animal and human—are responsible for about 1% of visits to emergency rooms. Bite injuries are more common during the summer months.

Closed-fist injury

In adults, the most common form of human bite is the closed-fist injury, sometimes called the "fight bite." These injuries result from the breaking of the skin over the knuckle joint when a person's fist strikes someone's teeth during a fight.

Causes and symptoms

In children, bite infections result either from accidents during play or from fighting. Most infected bites in adults result from fighting.
The infection itself can be caused by a number of bacteria that live in the human mouth. These include streptococci, staphylococci, anaerobic organisms, and Eikenella corrodens. Infections that begin less than 24 hours after the injury are usually produced by a mixture of organisms and can cause a necrotizing infection (causing the death of a specific area of tissue), in which tissue is rapidly destroyed. If a bite is infected, the skin will be sore, red, swollen, and warm to the touch.


In most cases the diagnosis is made by an emergency room physician on the basis of the patient's history.
Because the human mouth contains a variety of bacteria, the physician will order a laboratory culture to choose the most effective antibiotic.


Treatment involves surgical attention as well as medications. Because bites cause puncturing and tearing of skin rather than clean-edged cuts, they must be carefully cleansed. The doctor will wash the wound with water under high pressure and debride it. Debridement is the removal of dead tissue and foreign objects from a wound to prevent infection. If the bite is a closed-fist injury, the doctor will look for torn tendons or damage to the spaces between the joints. Examination includes x rays to check for bone fractures or foreign objects in the wound.
Doctors do not usually suture a bite wound because the connective tissues and other structures in the hand form many small closed spaces that make it easy for infection to spread. Emergency room doctors often consult surgical specialists if a patient has a deep closed-fist injury or one that appears already infected.
The doctor will make sure that the patient is immunized against tetanus, which is routine procedure for any open wound. A study released in June 2004 showed that routine use of antibiotics for human bites may not be necessary, as physicians try to minimize overuse of antibiotics. Superficial wounds in low-risk areas may no longer need antibiotic treatment, but more serious human bites to high-risk areas such as the hands should be treated with antibiotics to prevent serious infection. Patients with closed-fist injuries may need inpatient treatment in addition to an intravenous antibiotic.


The prognosis depends on the location of the bite and whether it was caused by a child or an adult. Bites caused by children rarely become infected because they are usually shallow. Between 15-30% of bites caused by adults become infected, with a higher rate for closed-fist injuries.


Prevention of human bite infections depends upon prompt treatment of any bite caused by a human being, particularly a closed-fist injury.



"Do All Human Bite Wounds Need Antibiotics?" Emergency Medicine Alert June 2004: 3.

Key terms

"Fight bite" — Another name for closed-fist injury.
Closed-fist injury — A hand wound caused when the skin of the fist is torn open by contact with teeth.
Debridement — The surgical removal of dead tissue and/or foreign bodies from a wound or cut.
Necrotizing — Causing the death of a specific area of tissue. Human bites frequently cause necrotizing infections.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Recent studies that did use culture methods for anaerobic bacteria indicate that anaerobes are far more prevalent in human bite infections than previously recognized.
For empiric parenteral therapy of human bite infections, the broadest aerobic-anaerobic coverage possible is needed, for example, penicillin-G plus a penicillinase-resistant penicillin or a first-generation cephalosporin.
[17] Manson ML, Koch SL: Human bite infections of the hand.
[19] Farmer CB, Mann RJ: Human bite infections of the hand.