AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Human bite wounds have a notorious reputation, which mostly is based on one injury, the closed-fist injury. Human bites in other areas pose no greater risk than animal bites. Three general types of injuries can lead to complications: (1) closed-fist injury, (2) chomping injury to the finger, and (3) puncture-type wounds about the head caused by clashing with a tooth. Otherwise, the general principles of contaminated wound management apply to human bite wounds.

Pathophysiology

In a closed-fist injury, forces sufficient to break the skin from striking an opponent's tooth often inoculate the extensor tendon and its sheath. Because the hand is flexed at the time of impact, the bacterial load is caudally transferred when the hand is opened and the tendon slides back to its relaxed state. The resulting contamination cannot be readily removed with normal cleansing and irrigation.

When a finger is bitten, such as in a chomping-type injury, tendons and their overlying sheaths are close to the skin. The wound may appear to be a minor abrasion-type injury, but careful inspection is required to rule out deep injury.

When a tooth strikes the head, even a deep puncture wound may appear innocuous. Deep, subgaleal, bacterial contamination is possible, especially true in young children who have relatively thin soft scalp and forehead tissue.

Frequency

United States

The exact incidence of human bite wounds is unknown, and many cases do not come to medical attention. The institutionalization of patients with poor impulse control creates a high-risk environment for human bite wounds. Lesch-Nyhan syndrome is an uncommon disorder that includes self-mutilation through biting.

Mortality/Morbidity

Although mortality is rare, morbidity can be significant, especially in closed-tissue spaces.

• The primary concern with human bites of the hand is infection, which can be severe because of spread along tendon sheaths and spread deep into the hand. Surgical incision and drainage may be needed. Resultant scarring and tissue damage may compromise normal function of the hand.
• Infection is also the major complication of bites in other areas of the body. Most infections can be treated adequately; however, infections of poorly vascularized structures, such as ear cartilage, may be difficult to treat.
• Other serious infectious complications, such as osteomyelitis of the skull vault, necrotizing fasciitis, and septic arthritis, are associated with human bites. Transmission of human immunodeficiency virus (HIV) is reported as a result of a human bite wound (see Medical Care).¹

Sex

Predominantly, males have this type of injury.

• Compared with females, males have a higher risk for bite wounds because they typically have a more aggressive nature.
• Closed-fist injuries almost exclusively occur in young males.

Age

Typically, young individuals are predisposed to this type of injury.

• Closed-fist injuries occur most often in adolescents and adults younger than 40 years.
• Toddlers frequently bite one another, but injuries usually are superficial and low risk.
• Penetrating tooth injuries of the scalp and forehead pose a higher risk to young patients than to older patients.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

• Although most patients present with no history of human bites, it is important to consider the possibility that the patient may not be telling the truth in cases of domestic disputes or criminal activities. Additionally, many patients may be inebriated and therefore not be the best historians.
• All injuries dorsal to the metacarpophalangeal (MCP) joint should be considered bite wounds until proven otherwise.
• • Patients' explanations for such wounds are often misleading; thus, extreme caution is necessary.
  • By carefully explaining of the need for an accurate history, the clinician may be able to elicit the truth from the patient. However, experienced emergency physicians often treat such injuries as bites regardless of the history.
  • Occasionally, patients with these injuries present to a dermatologist.
• Most bite wound infections are present at the initial emergency department (ED) visit. Patients may be referred to the dermatologist for follow-up care; therefore, dermatologists should be familiar with these injuries and with their treatment.
• • With closed-fist injuries, the initial injury often appears minor to the patient; thus, he or she does not seek care until infection develops.
  • To minimize complications in a child who receives a small laceration to the scalp or forehead during unwitnessed horseplay, carefully ascertain whether a tooth caused the wound.
• Other aspects of a patient's history that may influence care include the patient's tetanus immunization status, time delay from injury to presentation, disability, and underlying immunosuppressive disease.

Physical

• Physicians must be careful with any laceration overlying the MCP joint.
• • Additionally, physicians should carefully assess bite wounds of the fingers for deeper penetration into the tendon apparatus.
  • Extending the wound may be necessary to fully evaluate the underlying structures and the extent of injury.
• With specific bite wounds, the following should be assessed:
• • MCP wounds (closed-fist injuries) - Integrity of the extensor tendons, signs of infection, crepitation, and loss of knuckle height
  • Chomping injuries of the finger - Integrity of the extensor and flexor tendons and evidence of infection, including flexor tenosynovitis
  • Ear bites - Loss of tissue and violation of cartilage
  • Other bites - Tissue loss and depth of penetration

Causes

Typically, bite wounds are a result of fighting or altercations.

• As with most intentional injuries, human bites are often the result of an incident involving alcohol use.
• Domestic violence may be a factor.
• Child abuse may involve bite wounds from adults.
• Domestic violence and child abuse are most likely to be factors in patients examined by dermatologists, and these factors are the most important to rule out during the evaluation.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Hand infections
Child abuse (see (Pediatrics, Child Abuse)
Domestic violence (see Elder Abuse and Domestic Violence)

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Routine laboratory studies generally are not indicated because the injured population is usually young and healthy. The diagnosis of infection is based on clinical findings.
• Wound cultures may be helpful. Microbiologic findings in human bite wounds are fairly consistent, yet cultures are obtained if purulence is present in an untreated infected bite.

Imaging Studies

• Radiographs
• • In closed-fist injuries, an underlying metacarpal head fracture is possible. This may indicate the need for inpatient treatment.
  • Plain radiographs of infected bites of the hand of some duration may show evidence of osteomyelitis.
  • If the history indicates that a tooth was broken during the incident, radiography may be indicated to examine for a foreign body.

Procedures

• Wound care may be required.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

Prehospital care

Recovery of avulsed tissue parts (eg, ear, finger) is an important consideration for prehospital providers. As noted, many of these injuries are sent for evaluation by either the ED physician or a hand surgeon. Otherwise, the management of a human bite wound is generally uncomplicated and involves the application of a temporary dressing and patient transport.

ED care

Most infections resulting from bites are present at the patient's first visit. A patient who presents early with a noninfected bite requires individual evaluation to decide on treatment. Treatments for specific injuries include the following:

• Infected closed-fist injuries
• • Because of the deep nature of these infections and because of the relatively poor vascular supply to the tendons and other connective tissue, the patient be must be admitted to the hospital for intravenous antibiotic therapy.
  • Surgical drainage may also be necessary.
• Noninfected closed-fist injuries
• • An underlying fracture indicates inpatient treatment in certain circumstances.
  • After appropriate anesthesia is induced, explore the wound for joint-space violation or tendon injury. Involvement of the joint space is an indication to admit the patient.
  • Consider the admission of patients with tendon injuries; usually, these are present.
  • Proper wound assessment includes using a tourniquet and extending the wound as needed to improve visualization.
  • Provide outpatient treatment of these wounds only in consultation with a hand or orthopedic surgeon. Such care may include careful wound cleansing, antibiotic therapy, application of a bulky dressing or splint, and elevation of the affected part.
  • Early follow-up care is mandatory.
• Chomping injuries
• • As with closed-fist injuries, patients with infected wounds are generally admitted to the hospital for intravenous antibiotic therapy.
  • Treat noninfected wounds that appear to violate the tendon apparatus in the same manner as noninfected closed-fist injuries.
• Puncture wounds
• • Puncture wounds most commonly occur about the head.
  • Such wounds are difficult to adequately clean unless they are extended to allow effective irrigation.
  • In the absence of infection, such wounds are best left open and closed secondarily, if cosmetically necessary.
  • The use of antibiotics is debatable because, to the authors' knowledge, no large studies have been conducted to examine this type of wound. Because of the high infection rate in these wounds, a course of outpatient antibiotics is usually prescribed, with close follow-up care.
• Bites to the ear or nose
• • When associated with tissue loss, these wounds require consultation with a plastic surgeon or an ear, nose, and throat (ENT) physician.
  • Because of the poor blood supply to the cartilage and because of the difficulties in treating chondritis, seeking a consultation for a bite that violates the cartilage in these areas is prudent.
  • To the authors' knowledge, no placebo-controlled studies have been performed to examine these types of wounds, but common practice includes the use of prophylactic antibiotics.
• Superficial bites
• • When no significant penetration of the overlying skin is evident, human bites can be adequately managed with only local cleansing and tetanus immunization.
  • At clinical examination, these wounds appear as a mixture of abrasions and contusions.
• Wound involving possible HIV transmission
• • HIV transmission occurs only rarely after a human bite.
  • Exposure to saliva alone is not considered a risk factor for HIV (or hepatitis) transmission. Transmission requires the presence of HIV-infected blood in the saliva of the biter and a skin break on the victim.
  • The reverse consideration is also important. Blood from a patient who is infected with HIV could come into contact with the mucous membranes of the biter.
  • A 2005 US Centers for Disease Control and Prevention recommendation reported by Smith et al² states that postexposure prophylaxis with a 28-day course of highly active antiretroviral therapy should be used in both of these scenarios.
  • A blanket recommendation to administer prophylaxis in all cases is unwarranted. Each patient must be individually assessed before postexposure prophylaxis is administered.
• Other bite wounds
• • The treatment for deeper bite wounds to other areas is similar to that of other contaminated wounds. Delay suturing in such wounds unless adequate cleansing is possible.
  • As with animal bites, the hand is considered a high-risk area in human bites. In selecting the treatment, other factors to consider in include the cosmetic significance of the area, local blood supply, time delay to treatment, and host factors.
  • Usually, bite wounds to well-vascularized areas (eg, face) that can be adequately cleansed may be sutured primarily. When in doubt, delaying closure is best.
  • The use of antibiotics in these types of wounds does not decrease subsequent infection rates.

Surgical Care

• As discussed above, surgical care may be necessary if a closed-tissue infection occurs after the initial bite.
• The hand is extremely susceptible to a human-bite injury, and consultation with a hand surgeon may be needed to properly address this injury.

Consultations

• Consultation with a surgeon is indicated if evidence of an infection in a closed-tissue space (eg, hand) is present.
• Consultation with an infectious diseases specialist may also be necessary if infection is suspected.
• A hand and/or orthopedic surgeon should be consulted for infected human bites of the hand and bites involving a fracture, joint-space violation, or significant tendon injury. Consider consultation or the use of agreed-upon protocols for other human bites to the hand. Outpatient care of noninfected closed-fist injuries should be administered only in consultation with a hand or orthopedic surgeon.
• A plastic surgeon or ENT physician should be consulted for significant injuries to the special structures about the face and for wounds involving significant tissue loss.

Activity

Activity is determined on the basis of the area injured and the depth of penetration.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

The only drug therapy of significance in human bites is antibiotic treatment. The bacterial flora includes that of the mouth and skin. Theoretically, penicillin can be used to treat oral pathogens and may suffice for prophylactic treatment because Staphylococcus species probably infect bite wounds only secondarily.

To the authors' knowledge, no well-controlled studies have been conducted to investigate the use of antibiotics to prevent infection in human bite wounds. Uncontrolled studies have involved cephalosporins; generally, the findings do not indicate a benefit of prophylactic antibiotic treatment. This lack of definitive findings in the literature has led to recommendations for prophylaxis that are based on experience with infected human bite wounds. Therefore, expensive, broad-spectrum antibiotic therapy is commonly recommended instead of penicillin treatment.

Once a human bite is infected, beta-lactamase–producing staphylococci must be addressed. First-generation cephalosporins may not cover Eikenella corrodens. Additionally, Eikenella species are resistant to clindamycin, penicillinase-resistant semisynthetic penicillins, and metronidazole. Broad-spectrum antibiotic treatment, rather than combination therapy, is the usual choice for infected bite wounds. In 2003, Talan et al³ reported on an in vitro study of 50 infected human bites, which indicated that amoxicillin-clavulanic acid and moxifloxacin demonstrated excellent activity against common isolates. For patients who are allergic to penicillin, alternative treatments can also include moxifloxacin or erythromycin plus metronidazole. This treatment is not optimal, and, if it is used, follow-up should be conducted at 1 week to ensure it has been effective.

Drug Category: Antibiotics

Therapy must cover all likely pathogens in the context of the clinical setting.

Drug Category: Immunizing agents

These agents are used to immunize patients against tetanus.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• The need for inpatient care is determined by the severity of injury.
• Severe bites may necessitate inpatient services or, at the least, consultation with a surgeon; however, the need for this care is not typical.

Further Outpatient Care

• Patients with human bite wounds (other than superficial wounds) must undergo early follow-up care within 1-2 days.
• Provide outpatient treatment of noninfected closed-fist injuries only in consultation with a hand or orthopedic surgeon. Such care may include careful wound cleansing, antibiotic therapy, application of a bulky dressing or splint, and elevation of the affected part.

In/Out Patient Meds

• See Medication.

Transfer

• Transfer is determined on the basis of the following:
• • Signs and symptoms of infection or damage to deeper structures
  • The need for hand evaluation and/or consultation with a surgeon

Complications

• Infection and resulting sequelae are the main complications in human bites. These include serious soft-tissue infection, tendon damage, tissue contracture, and osteomyelitis.
• Cosmetic deformity may be a complication.
• Resultant scarring and tissue damage may compromise normal function of the hand.

Prognosis

• The prognosis is generally excellent, except for possible sequelae from serious infection.

Patient Education

• The most important educational aspect for the patient is related to follow-up care and the significant need to be aware of the potential for infection and/or other later complications.
• For excellent patient education resources, visit eMedicine's Bites and Stings Center. Also, see eMedicine's patient education article Human Bites.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Failure to elicit a careful history regarding the circumstances of a wound or to treat a human bite as a complicated laceration
• • If either of the aforementioned failures leads to a poor outcome, the physician can be at fault for obtaining an improper history.
  • A key point is that the physician must be extremely cautious with wounds over the MCP joints, with hand wounds in general, and with small lacerations about the head and forehead in young children.
  • Documentation of the mechanism reported is essential to avoid later questions regarding treatment.
• Failure to report suspected child abuse (Reporting is mandatory for health care professionals in most jurisdictions.)
• Medscape Medical Malpractice and Legal Issues Resource Center

Special Concerns

• As noted before, the hand and/or deeper structure damage is the main concern in cases of human bites.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

1. Pretty IA, Anderson GS, Sweet DJ. Human bites and the risk of human immunodeficiency virus transmission. Am J Forensic Med Pathol. Sep 1999;20(3):232-9. [Medline].
2. Smith DK, Grohskopf LA, Black RJ, Auerbach JD, Veronese F, Struble KA, et al. Antiretroviral postexposure prophylaxis after sexual, injection-drug use, or other nonoccupational exposure to HIV in the United States: recommendations from the U.S. Department of Health and Human Services. MMWR Recomm Rep. Jan 21 2005;54(RR-2):1-20. [Medline].
3. Talan DA, Abrahamian FM, Moran GJ, Citron DM, Tan JO, Goldstein EJ, et al. Clinical presentation and bacteriologic analysis of infected human bites in patients presenting to emergency departments. Clin Infect Dis. Dec 1 2003;37(11):1481-9. [Medline].
4. Baker MD, Moore SE. Human bites in children. A six-year experience. Am J Dis Child. Dec 1987;141(12):1285-90. [Medline].
5. Ball V, Younggren BN. Emergency management of difficult wounds: part I. Emerg Med Clin North Am. Feb 2007;25(1):101-21. [Medline].
6. Bunzli WF, Wright DH, Hoang AT, Dahms RD, Hass WF, Rotschafer JC. Current management of human bites. Pharmacotherapy. Mar-Apr 1998;18(2):227-34. [Medline].
7. Chen E, Hornig S, Shepherd SM, Hollander JE. Primary closure of mammalian bites. Acad Emerg Med. Feb 2000;7(2):157-61. [Medline].
8. Donkor P, Bankas DO. A study of primary closure of human bite injuries to the face. J Oral Maxillofac Surg. May 1997;55(5):479-81; discussion 481-2. [Medline].
9. Gilbert DN, Moellering RC, Sande MA. Human bites. In: The Sanford Guide to Antimicrobial Therapy. 30^th ed. Hyde Park, Vt: Antimicrobial Therapy; 2000:37.
10. Kelly IP, Cunney RJ, Smyth EG, Colville J. The management of human bite injuries of the hand. Injury. Sep 1996;27(7):481-4. [Medline].
11. Lindsey D, Christopher M, Hollenbach J, Boyd JH, Lindsey WE. Natural course of the human bite wound: incidence of infection and complications in 434 bites and 803 lacerations in the same group of patients. J Trauma. Jan 1987;27(1):45-8. [Medline].
12. Miura I, Ohshima A, Takahashi N, Hashimoto K, Nimura T, Utsumi S, et al. A new non-random chromosomal translocation t(3;6)(q27;p21.3) associated with BCL6 rearrangement in two patients with non-Hodgkin's lymphoma. Int J Hematol. Oct 1996;64(3-4):249-56. [Medline].
13. Nakamura Y, Daya M. Use of appropriate antimicrobials in wound management. Emerg Med Clin North Am. Feb 2007;25(1):159-76. [Medline].
14. Schweich P, Fleisher G. Human bites in children. Pediatr Emerg Care. Jun 1985;1(2):51-3. [Medline].
15. Smith PF, Meadowcroft AM, May DB. Treating mammalian bite wounds. J Clin Pharm Ther. Apr 2000;25(2):85-99. [Medline].
16. Staiano J, Graham K. A tooth in the hand is worth a washout in the operating theater. J Trauma. Jun 2007;62(6):1531-2. [Medline].

Article Last Updated: Nov 12, 2008