Human Bites: Facts and Fiction

Abstract & Commentary

Synopsis: Infection rates in low-risk human bites are exceedingly low. Antibiotic treatment may not be necessary for these patients.

Source: Broder J, et al. Am J Emerg Med. 2004;22:10-13.

This study was aimed at evaluating the need for antibiotic therapy in low-risk human bite wounds. It was designed as a prospective, placebo-controlled, double-blinded study and was performed over a 4-year period of time at a major academic urban emergency department. Those patients that had human bites were eligible for inclusion except those who had them in high-risk areas (ie, hands, feet, cartilaginous structures). Patients were also excluded if they had puncture wounds or any wound that was penetrating deeper than the epidermis. Those patients sustaining low-risk human bite wounds were assigned by Broder and associates into either the placebo group or a 5-day course of antibiotics (cephalexin/penicillin).

Patients were instructed to return at 48 and 96 hours after their initial visit to the emergency department. Assessment for signs of infection including erythema, warmth, tenderness, lymphangitis, induration, purulent discharge and fever were documented. Means, proportions, and 95% confidence intervals were use to analyze and detect differences between both groups.

A total of 127 patients were enrolled in this study and 125 of them completed the study protocol. The median age was 32 years. Infection developed in only one of the 62 patients that received the placebo and none of the 63 patients that received the antibiotic. No difference was found between the medication compliance among the groups. Broder et al suggest limiting antibiotic usage for those patients with low-risk human bite wounds.

Comment by Joseph Varon, MD, FACP, FCCP, FCCM

Human bites are quite common. Indeed, it has been estimated that nearly half of all people in this country will experience a canine, feline or human bite during the course of their lifetimes.1 The cost of treating these patients is also exceedingly high and estimated at 100 million US dollars per year.2 The study by Broder et al is important as it presents interesting and compelling data against the routine use of antibiotics for low-risk human bites.3 Most standard textbooks still recommend antibiotic treatment routinely for all human and nonhuman bites. The 1.6% risk of infection in the placebo group is substantially lower than what has previously been reported.

This study supports a change in practice standards for low-risk human bites. However, the reader must understand that most patients in this study had superficial abrasion or dental impressions. Prior studies have reported a substantially higher rate of infections, mostly because they involved puncture wounds and lacerations.4

Clinicians caring for patients with low-risk human bites must consider each patient individually and based on the results of the study by Broder et al, withhold antibiotic therapy as long as close follow up is available.


1. Marr JS, et al. Public Health Rep. 1979;94:514-521.

2. Goldstein EJ. Clin Infect Dis. 1992;14:633-638.

3. Broder J, et al. Am J Emerg Med. 2004;22:10-13.

4. Malinowski RW, et al. J Trauma. 1979;19:655-659.

Dr. Varon is Professor at the University of Texas Health Science Center, Houston Tex.