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Author: Kinga Ensing, 5th Year Medical Student, University of Auckland, New Zealand; Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, April 2015.
A human bite occurs as the result of human teeth penetrating skin. This can happen on purpose if someone forcibly bites down on another person’s flesh or it can happen as an accident. Human bites have a high rate of infection.
The area of the bite will most likely be painful and tender to touch. The bite results in a semi-circular or oval red patch and may have bruising associated with it.2
Children often have bite wounds as a result of rough play. The wounds are usually located on face, upper arms and trunk. If bite mark has an inter-canine distance of 3 cm or more, consider abuse from an adult.2
Adolescents typically have closed fist injuries where the teeth have scratched the knuckles. These often present as small lacerations particularly over the third and fourth metacarpophalangeal joints or the proximal interphalangeal joints of the dominant hand.2
Signs of infection include:1
Human bites have higher infection risk than animal bite wounds. This is because of the extensive bacterial flora of the human mouth and skin. One study found that in 50 patients that had an infected human bite, on average, four isolates were cultured per wound. Pathogens in human bite wounds included both aerobic and anaerobic bacteria such as:3
Complications that can arise from a bite wound infection include:1
One retrospective study found that bite wounds which were greater than 3 mm or punctured had a threefold increase in infection compared to other wounds.4
Wounds that have not penetrated the skin are not a cause of concern unless abuse is suspected; the resulting bruising will heal on its own.
Patients with infected bite wounds on initial evaluation need to be sent to hospital for assessment and appropriate therapy.5
Even if a bite wound does not look infected, prophylactic oral antibiotics for 3–5 days are recommended, especially if:
If signs of infection are found on follow up, the course of antibiotics can be extended and swabs repeated.5 The agent of choice is amoxicillin-clavulanate. Alternative agents include a combination of an antibiotics with activity against Eikenella corrodens (eg doxycycline) and an antibiotic with anaerobic activity (eg metronidazole).6
Tetanus immune globulin and tetanus toxoid should be offered to patients with less than two primary immunisations. Those without a recent booster (last five years) can be offered the tetanus toxoid alone.5
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