What are the signs and treatment of anaphylaxis from a bee sting?

Signs and Symptoms of Anaphylaxis from Bee Stings

Anaphylaxis from bee stings presents with sudden onset (within minutes to 2 hours) of multi-system symptoms including skin manifestations (hives, flushing, swelling), respiratory compromise (throat tightness, stridor, wheeze, difficulty breathing), cardiovascular collapse (hypotension, tachycardia, weak pulse, dizziness, syncope), and gastrointestinal symptoms (crampy abdominal pain, vomiting, diarrhea). 1, 2

Cutaneous and Mucosal Signs

• Skin reactions include itching, redness, hives, or swelling that extends beyond the sting site 1
• Oral and nasal mucosa show itching and swelling 1
• Conjunctival involvement presents with itching, swelling, and redness 1
• Facial swelling extending beyond the sting site indicates systemic involvement rather than simple local reaction 3
• Notably, hives are absent in 20-30% of anaphylaxis cases, so their absence does not rule out anaphylaxis 4

Respiratory Signs

• Upper airway symptoms include hoarseness, throat itching, throat tightness, and stridor 1
• Lower airway manifestations present as cough, difficulty breathing, chest tightness, wheeze, and cyanosis 1
• Laryngeal edema is the most common cause of death from Hymenoptera-induced anaphylaxis 5
• Oropharyngeal stings (such as to the back of throat) carry particularly high risk of life-threatening airway obstruction from localized swelling 6

Cardiovascular Signs

• Circulatory compromise manifests as tachycardia, chest pain, hypotension, weak or thready pulse 1, 2
• Shock symptoms include dizziness, collapse, incontinence, and syncope 1, 2
• Cardiac anaphylaxis can cause arrhythmias, bradycardia, or chest pain with ECG changes 4
• Flushing and apprehension are early warning signs 2

Gastrointestinal Signs

• GI symptoms include nausea, crampy abdominal pain, persistent vomiting, and diarrhea 1
• These symptoms are more common with food-induced anaphylaxis but can occur with insect stings 4
• Involuntary voiding may occur in severe cases 2

Neurological Signs

• Central nervous system manifestations include behavioral changes (particularly in infants), sense of doom, headache, altered mental status, confusion, and tunnel vision 1
• Convulsions can occur in severe cases 2

Critical Timing and Presentation Patterns

• Onset is typically rapid: 70% of sting-induced anaphylaxis begins within 20 minutes and 90% within 40 minutes 4
• Rapid onset correlates with greater severity of reaction 4
• Only a few symptoms may be present during an episode, and symptoms can differ between patients and even between episodes in the same patient 1
• More than one body organ system is typically involved in anaphylaxis 1

Distinguishing Anaphylaxis from Large Local Reactions

• Large local reactions cause extensive erythema and swelling confined to tissues contiguous with the sting site, lasting over 24 hours 1
• Systemic reactions involve generalized signs and symptoms affecting organs distant from the sting site 1
• The presence of a stinger does not definitively identify a honeybee sting, as yellow jackets and other insects can also leave stingers 1

Special Considerations

• Fire ant stings produce a pathognomonic sterile pseudopustule within 24 hours 1
• Multiple stings (>100) can cause toxic reactions from massive envenomation that mimic anaphylaxis but result from direct venom effects rather than allergic mechanisms 7, 3
• Biphasic reactions (recurrence of symptoms hours later without re-exposure) occur in approximately 23% of drug/biological reactions but are less common with insect stings (6% of mixed-cause anaphylaxis) 4

Risk Factors for Severe or Fatal Reactions

• Coexisting asthma (especially if severe or poorly controlled) significantly increases risk 1
• Adolescence is associated with higher fatality rates 1
• Delay in epinephrine administration is strongly associated with fatal outcomes 1
• Older age and cardiovascular disease increase perioperative anaphylaxis fatality risk 1
• Mast cell disorders (found in 3-5% of sting anaphylaxis patients) predispose to very severe reactions 8

Treatment of Bee Sting Anaphylaxis

Immediately administer intramuscular epinephrine 0.3-0.5 mg in adults (0.01 mg/kg up to 0.3 mg in children) into the anterolateral thigh and activate emergency medical services—this single intervention is the most critical life-saving action. 7, 1

Immediate First-Line Treatment

• Inject epinephrine intramuscularly in the mid-outer thigh (vastus lateralis muscle) as soon as anaphylaxis is recognized 1, 7
• Intramuscular injection in the anterolateral thigh achieves faster and higher plasma concentrations than subcutaneous or arm injections 7, 3
• Adult dose: 0.3-0.5 mg depending on reaction severity 7, 3
• Pediatric dose: 0.01 mg/kg (maximum 0.3 mg in prepubertal children, up to 0.5 mg in teenagers) 1, 7
• Call emergency services immediately after administering epinephrine, without delay 7

Stinger Removal

• Remove the stinger immediately by scraping or flicking it away with a fingernail or tweezers to prevent additional venom injection 7, 5
• Venom can continue to be delivered for up to 60 seconds if the stinger remains 5

Patient Positioning

• Position the patient supine with legs elevated if hypotension develops, to prevent sudden death from "empty-ventricle syndrome" 7, 3
• Never allow standing, walking, or running during anaphylaxis 1
• Place in a position of comfort if there is respiratory distress and/or vomiting 1

Repeat Dosing and Escalation

• Be prepared to repeat epinephrine every 5-15 minutes if symptoms persist or worsen 1, 7
• Delayed or inadequate epinephrine use is associated with fatal outcomes 1, 7
• For refractory hypotension despite multiple IM doses, transition to intravenous epinephrine infusion: 1 mg epinephrine in 250 mL D5W, infused at 1-4 mcg/min, titrating up to 10 mcg/min in adults 7
• Administer 1-2 liters of IV normal saline bolus for persistent hypotension, as massive fluid shifts occur during anaphylaxis 7

Adjunctive Treatments (Only After Epinephrine)

• Supplemental oxygen should be given to all patients with prolonged reactions, hypoxemia, or requiring multiple epinephrine doses 7
• Inhaled albuterol (2.5 mg nebulized) for bronchospasm that persists despite epinephrine 7
• H1 antihistamines (diphenhydramine 25-50 mg IV/IM in adults) and H2 blockers (ranitidine 50 mg IV or famotidine 20 mg IV) as adjuncts, but these do not treat life-threatening symptoms 7, 3
• Corticosteroids (methylprednisolone 125 mg IV or prednisone 0.5 mg/kg PO) to potentially prevent biphasic reactions, though they have no immediate effect 7, 3

Critical Pitfalls to Avoid

• Never delay epinephrine administration—antihistamines and corticosteroids are not substitutes and delayed epinephrine is associated with fatal outcomes 7, 1
• Do not use subcutaneous epinephrine or inject in the arm, as intramuscular injection in the thigh is superior 7
• Do not assume the reaction is over after initial improvement, as biphasic reactions can occur hours later 7
• Avoid raising the patient to upright position during shock; maintain supine position with legs elevated 7
• Do not mistake swelling for infection and inappropriately prescribe antibiotics instead of focusing on anti-inflammatory treatment 5

Special Circumstances

• Eye stings require immediate ophthalmology evaluation, as they can cause permanent vision loss 7, 3
• Oropharyngeal stings (throat/mouth) require immediate endotracheal intubation and mechanical ventilation for at least 24 hours in patients with signs of airway compromise 6, 5
• Patients on beta-blockers may be refractory to epinephrine and require higher doses or alternative vasopressors like glucagon 7
• There are no contraindications to epinephrine in anaphylaxis, even in patients with cardiovascular disease, as the benefits far outweigh risks 7

Observation Period

• Monitor for biphasic reactions for 4-12 hours depending on risk factors for severe anaphylaxis 9, 10
• Biphasic reactions rarely occur without initial hypotension or airway obstruction 4
• Mandatory observation periods are not necessary for all patients, as biphasic reactions are difficult to predict and may occur outside typical observation periods 10

Discharge and Follow-Up

• Prescribe epinephrine autoinjector (EpiPen or equivalent) before discharge and demonstrate proper use 7, 3, 5
• Refer all patients to an allergist-immunologist for venom-specific IgE testing and consideration of venom immunotherapy, which dramatically reduces risk of future anaphylaxis 7, 3, 5
• Venom immunotherapy can reduce the risk of future systemic reactions from 25-70% to nearly zero 1
• Educate on trigger avoidance: avoid walking barefoot outdoors, wear protective clothing, avoid bright colors and floral patterns, eliminate scented products, and have nests professionally removed 7, 3

Treatment of Large Local Reactions (Non-Anaphylactic)

• Cold compresses help reduce local pain and swelling 1, 3
• Oral antihistamines and analgesics reduce itching and pain 1, 3
• Short course of oral corticosteroids in severe cases to limit swelling 1
• Antibiotics are usually not necessary, as large swelling in the first 24-48 hours is caused by allergic inflammation, not infection 1
• Fire ant pseudopustules should be left intact and kept clean 1