Textbook of Urgent Care Medicine, Chapter 39, Bites and Stings

Published on November 5, 2026

Original author: John Shufeldt

Originally published in 2014. Substantially updated and clinically reviewed in 2026.

INTRODUCTION

Bites and stings account for a significant number of visits to emergency departments and urgent care centers. Although the scope of this chapter does not lend itself to addressing all forms of bites, the most common bites that present to urgent care centers are discussed.

The urgency of treatment depends on the risk of infection, tissue or neurovascular injury, rabies or tetanus exposure, and systemic allergic or toxic effects. These distinctions determine which patients may be treated in urgent care and which require emergency transfer.

PRESENTATION

Cat bites are commonly puncture wounds, and the majority involve the fingers, hand, and forearm. Even small wounds may penetrate deeply and produce infection, particularly in the hand.
Dog bites commonly cause lacerations, punctures, and crush injuries. The risk of infection increases with deep wounds, delayed evaluation, hand involvement, and host factors such as immunocompromise.
Human bites are also a common presenting complaint in urgent care centers. Human bites can result from a clenched fist injury or an actual bite wound. Human bites produce a crush type of injury and have a high incidence of infection secondary to contamination from oral flora.
Bees, stinging ants, and wasps are members of the order Hymenoptera. Stings may result in local or generalized reactions or both. Most of the true allergic reactions occur from wasp, hornet, and yellow jacket stings.
Bites or stings from fire ants, brown recluse spiders, black widow spiders, and scorpions are less commonly encountered in an urgent care center.

TRIAGE PEARLS

Control bleeding.
Evaluate distal pulses.
Assess and immediately treat any signs of anaphylaxis:
- Airway compromise
- Hypotension
- Tachycardia
- Tachypnea
- Wheezing
- Abdominal pain
- Chest pain
Anaphylaxis is a clinical emergency. Give epinephrine intramuscularly into the mid-outer thigh immediately (1 mg/mL solution, 0.01 mg/kg; maximum 0.5 mg in adults and generally 0.3 mg in children), activate EMS, and support the airway and circulation. Repeat epinephrine in 5 to 15 minutes if needed. Antihistamines and corticosteroids are not substitutes for epinephrine.
Check for neurologic or mental status changes.
Immediate EMS transfer is indicated for airway symptoms, shock, rapidly progressive systemic reaction, severe envenomation, or suspected deep hand-space infection. Do not delay epinephrine or transfer to obtain laboratory testing.

HISTORY PEARLS

It is important to record the time of the event. The longer the delay in treatment, particularly for bites, the higher the incidence of infection.
Record the animal or insect species when known; whether the event was witnessed; location and depth of injury; prior allergy or anaphylaxis; immunocompromising conditions; pregnancy; current medications; and tetanus vaccination history.
For mammalian bites, record whether the animal is available for observation or testing, its health and vaccination history when known, the location of the exposure, and whether public health has been contacted.
Anaphylaxis usually begins rapidly after a sting, but onset and progression vary. A delayed or recurrent reaction remains possible; time since exposure does not exclude serious allergy.
Patients who experience a fire ant sting will initially develop a papule, which will evolve into a sterile pustule within the first 24 hours. Pustules can become necrotic with resultant scarring.
A suspected brown recluse bite may initially be only mildly erythematous. Some lesions become necrotic over the next few days, although many bites do not progress to necrosis.
Patients with black widow spider bites may experience severe fluctuating pain for up to 3 days after the bite.
Patients with scabies will report intense itching.
In a patient presenting with a laceration or crush injury at the second or third metacarpophalangeal (MCP) joint, particular concern must be taken to identify whether it is a clenched fist injury from punching a tooth.
An unprovoked bite, an ill or unavailable animal, a bat encounter, or an exposure in a region with endemic rabies increases the need for prompt public health risk assessment. A seemingly minor bite does not itself exclude rabies risk.

PHYSICAL EXAM PEARLS

Hymenoptera

The most common physical exam findings in patients with Hymenoptera envenomation are slight erythema, local edema, pruritus at the sting site, and pain.
Large local swelling may expand over 24 to 48 hours without bacterial infection. Its size does not, by itself, establish or predict anaphylaxis. Evaluate for generalized urticaria, respiratory symptoms, hypotension, gastrointestinal symptoms, and altered mental status.
Anaphylaxis is a true allergic reaction and may present with symptoms ranging from mild to fatal.

Brown Recluse Spiders

Often, the bite of a brown recluse spider goes unnoticed. Symptoms may not start until 1 to 2 days after envenomation.
Localized injury may progress from erythema to blistering, discoloration, or necrosis. However, many other skin disorders resemble a brown recluse bite. Avoid labeling an unwitnessed necrotic lesion as spider envenomation without considering bacterial infection and other diagnoses.
Systemic symptoms such as fever, dark urine, jaundice, or weakness after a suspected bite require emergency assessment for possible hemolysis or other toxicity.

Black Widow Spiders

This local pain may be followed by:
- Generalized severe muscle cramps
- Abdominal pain that can mimic peritonitis
- Weakness
- Tremor
In severe cases, there may be nausea, vomiting, syncope, chest pain, or respiratory difficulties.

Scorpion Stings

Envenomation from the bark scorpion causes a severe, immediate burning pain and stinging. Often, no bite marks are noticed.
In children, severe neurotoxic effects may include roving eye movements, muscle twitching, drooling, agitation, difficulty swallowing, or respiratory distress. Call Poison Control promptly (1-800-222-1222) and arrange emergency transfer for systemic findings.

Scabies and Body Lice

Scabies infestation causes intense pruritus, often worse at night, with papules and thin burrows. Common sites include finger webs, wrists, waist, genitals, and other flexural surfaces. The diagnosis is not based on a solitary insect bite.
Body lice can cause intensely pruritic papules and excoriations, often on the trunk and at clothing contact sites. Check clothing seams for lice and nits. Pubic lice are a separate infestation and should not be equated with body lice.

Human Bites

The most common bite injury is secondary to a clenched fist injury when the second or third MCP joint contacts the tooth of another individual.
Patients with bites from clenched fist injuries must be examined for full range of motion, tendon involvement, and neurovascular status.
The exam in a patient with a clenched fist injury must also include evaluation of the joint space. Any injury in the vicinity of the MCP joint should be treated as though it is secondary to a clenched fist injury.
Examine the wound with the hand in both flexion and extension to expose tendon or joint penetration that may be hidden when the fist is opened. Any suspicion for joint-capsule, tendon, or deep-space involvement warrants emergency hand-surgery evaluation.

TESTING PEARLS

For bites caused by humans, cats, and dogs, radiographs may be helpful when a foreign body is expected.
Obtain radiographs when fracture, tooth fragment, deep puncture, or bone or joint involvement is suspected. Ultrasonography or advanced imaging may be required at a receiving facility for deep infection or occult retained material.
Routine testing is generally unnecessary for uncomplicated localized Hymenoptera or fire ant stings and mild spider bites. Findings suggesting systemic toxicity change this approach.
Laboratory studies are not routine in uncomplicated local reactions. Systemic envenomation, suspected hemolysis, sepsis, or severe allergic reactions require emergency-level evaluation and testing as indicated.

DIAGNOSIS PEARLS

The key to diagnosis for bites caused by humans, cats, and dogs is generally found in the medical history. In patients with human bites caused by a clenched fist injury, the patient may not realize that they in fact have a human bite, or they may not be willing to admit that they punched someone in the mouth.
Most patients are aware when they have been stung by wasps, bees, or stinging ants; thus the diagnosis is not elusive.
Scorpion stings in children and particularly in infants can be diagnostically challenging. Oftentimes, parents bring in a child who is in acute distress and yet no discernible etiology can be determined.
The clinical diagnosis of anaphylaxis rests on an acute, compatible constellation of systemic symptoms. Skin findings may be absent; do not delay treatment for laboratory confirmation.
Consider cellulitis, abscess, necrotizing infection, vasculitis, and other skin disorders before diagnosing a brown recluse bite on the appearance of a wound alone.

TREATMENT AND DISPOSITION PEARLS

All bite wounds should be copiously irrigated with normal saline or tap water only. More toxic solutions like chlorhexidine (Hibiclens) should never be used for irrigation of puncture wounds or bites. Devitalized tissue should be excised.
Control bleeding, irrigate and inspect the wound, assess tendon and neurovascular function, and remove accessible foreign material. Deep punctures or wounds near hand joints may require specialist exploration rather than office closure.
Primary closure is an individualized decision. Clean, low-risk facial dog bites may be closed after adequate irrigation; deep punctures, clenched-fist injuries, infected wounds, and many hand bites should generally be left open or managed after specialty evaluation.
Tetanus prophylaxis should be given when indicated.
Treat animal and human bites as dirty or major wounds for tetanus assessment. In a patient with a completed primary series, a booster is indicated if the last tetanus-containing vaccine was at least 5 years ago. Give tetanus immune globulin when indicated by incomplete/unknown vaccination or specified immunodeficiency; follow CDC guidance.
For patients assessed as needing rabies postexposure prophylaxis, coordinate urgently with public health and a facility able to administer it. For a previously unvaccinated, immunocompetent person, CDC recommends wound care, human rabies immune globulin, and vaccine on days 0, 3, 7, and 14; those with immune disorders also receive a day-28 vaccine dose. Previously vaccinated patients receive vaccine on days 0 and 3 without immune globulin.

Table 1. Mammalian Bite Management in Urgent Care

Exposure	Prophylaxis and treatment considerations	Disposition
Cat bite penetrating skin, particularly hand	Offer oral antibiotic prophylaxis if blood drawn or deep puncture; cover Pasteurella and anaerobes.	Same-day evaluation for deeper structure involvement; follow-up within 24-48 hours if outpatient.
Dog bite	Select prophylaxis for puncture/crush wounds, hand/face, deep injury, significant contamination, or high-risk host.	Close selected clean low-risk wounds; ED for deep tissue/vascular injury or systemic infection.
Human bite / clenched-fist injury	Prophylaxis for bleeding bites; irrigate and assess for Eikenella, anaerobes, tendon or joint penetration.	Urgent ED/hand surgery evaluation for any suspected fight bite over MCP joint.
Antibiotic example (adult, no contraindications)	Amoxicillin-clavulanate 875/125 mg orally every 12 hours when prophylaxis/treatment indicated. Often 3-5 days prophylaxis or 5-7 days uncomplicated infection; adjust to clinical response, local guidance, allergy and renal function.	Avoid using clindamycin alone for cat or human bites; obtain alternatives that cover appropriate organisms.

Illustrative adult regimen only; pediatric and pregnancy dosing require individualized selection. Infection involving joint, tendon, bone, or systemic illness requires hospital care.

Cat Bites

Cat bites have a substantial risk of infection, especially when punctures penetrate the hand. Pasteurella multocida and mixed oral flora are important pathogens. Offer prophylaxis for bites that penetrate the skin and draw blood or may be deep.
Amoxicillin-clavulanate is the antibiotic of choice for cat bites.
A penicillin-allergic patient requires an alternative regimen with Pasteurella and anaerobic coverage selected for age, pregnancy, allergy type, and local guidance. Routine cefuroxime or doxycycline monotherapy should not be assumed adequate in every circumstance.

Dog Bites

Initial primary closure may be considered for selected, well-cleaned, low-risk wounds, particularly on the face, after adequate assessment of deep injury and infection risk.
Puncture wounds to the hands and feet should initially be left open.
The antibiotic of choice is amoxicillin-clavulanate.
Not every superficial, low-risk dog bite requires prophylaxis. Avoid routine antibiotics for bites that have not broken skin; select prophylaxis based on wound and host risk. If signs of spreading infection or systemic symptoms develop, refer for hospital-level assessment.

Human Bites

As with other bites, human bites should initially be treated with copious irrigation and debridement.
Generally speaking, human bites should be left open.
The drug of choice for human bites is amoxicillin-clavulanate.
Patients with clenched-fist injuries should not be managed solely with a 24-hour recheck when joint, tendon, or capsule penetration is possible; splint, cover the wound, and arrange urgent specialist/emergency assessment.

Hymenoptera Stings

In bee stings, the stinger should be removed and the area cleansed.
Swelling and erythema caused by Hymenoptera stings are difficult to distinguish from cellulitis; however, infection from bee stings is exceedingly rare.
Minor local reactions can be treated with oral antihistamines and analgesics.
A larger local reaction may benefit from cool compresses and oral antihistamines; antibiotics are not indicated in the absence of infection.
For anaphylaxis, give intramuscular epinephrine immediately and arrange emergency monitoring and transfer. Antihistamines may relieve itching after epinephrine but do not treat airway or circulatory compromise. Patients at risk of recurrence need an epinephrine autoinjector plan and allergy follow-up.

Black Widow Spider Bites

Local wound treatment is indicated.
Severe muscle cramping, uncontrolled pain, vomiting, hypertension, or respiratory symptoms require ED evaluation and Poison Control consultation. Benzodiazepines, parenteral analgesia, and antivenom are hospital-level decisions in selected severe cases.

Brown Recluse Spider Bites

Clean the lesion, apply a cool compress and nonadherent dressing, address tetanus status, and arrange reassessment. Routine systemic antibiotics or early extensive excision are not indicated for venom injury without bacterial infection; systemic illness warrants emergency evaluation.

Scorpion Stings

Treatment includes local wound care, analgesia, and ice.
Call Poison Control (1-800-222-1222). Children with abnormal eye movements, excessive secretions, muscle jerking, agitation, or breathing/swallowing difficulty require rapid ED transfer; antivenom for severe Centruroides envenomation is administered in hospital.

Infestations

Scabies: Permethrin 5% cream is a first-line prescription treatment for classic scabies in eligible patients. Apply according to product guidance; a second application about a week later may be needed. Treat close contacts simultaneously and wash or isolate relevant linens and clothing.
Body lice: Regular bathing, clean clothing and laundering of bedding/clothing with hot washing and drying are usually sufficient. Pediculicides are only occasionally necessary. Do not routinely prescribe the same treatment schedule used for scabies.

Table 2. Urgent Care Disposition for Bites and Stings

Clinical finding	Recommended action
Anaphylaxis, airway or breathing compromise, hypotension, collapse	Give intramuscular epinephrine immediately; activate EMS, stabilize, and transfer.
Clenched-fist hand bite, suspected tendon/joint invasion, deep space infection, necrotizing infection	Cover wound, immobilize, and arrange urgent ED/hand-surgery assessment.
Potential rabies exposure: bat or high-risk wildlife; ill/unavailable mammal	Immediate public health risk assessment and timely referral for rabies PEP if indicated.
Severe widow-spider envenomation, systemic brown recluse illness, neurologic scorpion toxicity	Consult Poison Control; ED/EMS disposition according to severity.
Uncomplicated low-risk wound, local sting, uncomplicated infestation	Treat in urgent care, document warning signs and a defined follow-up plan.

EMS = emergency medical services; ED = emergency department; PEP = postexposure prophylaxis.

MEDICOLEGAL PEARLS

Human bites have a very high incidence of infection. Clenched fist injuries can be complicated by extensor tendon tenosynovitis, septic arthritis, osteomyelitis, and simple cellulitis. Infections from both human and dog bites are often polymicrobial, so appropriate prophylactic antibiotic coverage is important.
Although wild animals account for the vast majority of rabies cases, dog, cat, and other mammalian bites should be reported to state or local officials, who should be consulted regarding the prevalence of rabies in the local animal population.
Bat exposure, even without evidence of a documented bite, may warrant rabies prophylaxis.
When a healthy dog, cat, or ferret is available, the local public health authority can arrange 10-day observation when appropriate; wildlife and bat exposures require different risk pathways. Do not assume the absence of a visible bite rules out an exposure.
Document the species, wound site and depth, neurovascular/tendon examination, irrigation, immunizations, prophylaxis decisions, return precautions, and communications with public health or Poison Control. Failure to document reassessment and disposition can obscure the clinical decision-making.