II. Epidemiology

  1. Peak Incidence in August
  2. Hymenoptera are most common cause of serious venom reaction (as well as for death) in U.S.
    1. Systemic Allergic Reaction: 5% of patients
    2. Anaphylaxis: <1% of patients overall (up to 3% in adults)
      1. Hymenoptera Stings are responsible for 17% of U.S. anaphylactic reactions overall
      2. Responsible for average of 62 deaths per year in U.S.

III. Types: Hymenoptera

  1. Hymenoptera order contains more than 100,000 species, of which only the Stinging Insects are listed here
  2. Usually only Insects of Hymenoptera cause Anaphylaxis
    1. Distinct InsectVenoms (allergy specific to the 5 types below)
  3. Yellow jackets and Wasps (Vespidae family)
    1. Attracted to food and garbage containers
    2. Attack without provocation
    3. Stings peak in summer and autumn coinciding with population peaks
    4. Yellow jackets nest in the ground (crevices or burrows) or in trees or shrubs
    5. Wasps nest under houses, in barns, mailboxes, shrubs and tree cavities
    6. Disturbance of a nest may lead to attacks (>10)
  4. Hornets (Vespidae family)
    1. Nest on undersurfaces of decks and roof overhangs
    2. Attack in small groups (1-5) if nest disturbed
    3. Hornet venom is more potent and of greater volume, able to reach lethal levels with fewer stings
    4. Associated with higher risk of multiorgan failure and death than with other stinging Hymenoptera
  5. Bumblebees and Honeybees (Apidae family)
    1. Not aggressive unless hives attacked
    2. Honey Bees (Apis) leaves a detached Stinger in the skin, and then dies shortly thereafter
    3. Bumble Bees (Bombus) do not detach their Stinger, and may sting multiple times
  6. Africanized Honeybees (Killer Bees)
    1. Attack in swarms of hundreds
    2. Pursue victims well away from the hive
    3. In U.S. found in Arizona, California, Nevada, New Mexico and Texas
  7. Fire Ants (Formicidae family, Solenopsis species)
    1. Fire ants are 3 to 8 mm and red-brown or black
    2. Nest in the ground
    3. Attack in swarms when nest is attacked, most typically on extremities
    4. Circular cluster of 6 to 7 stings is common
    5. Stings may result in immediate and delayed Hypersensitivity Reactions

IV. History

  1. Prior prior Allergic Reaction history (including Insect sting reactions)
  2. Current sting attack history
    1. Events leading up to the sting
    2. Number of sting sites and their location
    3. Stinging Insect species (see above, if patient able to identify)

V. Signs: Local Reactions

  1. Most reactions have onset in minutes and hours and resolve within 24 hours
  2. Bees/Wasps (Venom contains biogenic amines)
    1. Erythematous Papules develop in seconds
    2. Most lesions subside in 4-6 hours
    3. Larger areas of edema and Urticaria may develop (10%, lesions may last >48 hours)
    4. Some extensive local reactions persist for days
  3. Fire ants (Venom contains alkaloids)
    1. Arc shaped lesions or circular grouping of 6-7 stings
    2. Sterile Pustules develop within 24 hours
  4. Honeybee
    1. Barbed Stinger remains in skin after sting
      1. Injection continues until Stinger removed (although most venom is injected in first minute)
      2. Do NOT grasp Stinger - will inject more venom
      3. Retained Stinger may also lead to Foreign Body Granuloma and risk for secondary infection
    2. Technique to remove Stinger
      1. Scrape sharp object (knife) horizontally over skin
      2. Drags Stinger out intact

VI. Signs: Large Local Reaction

  1. Represents 19% of reactions
  2. Onset in first few days and resolves by 7 days after sting
  3. Erythema and induration >10 cm (>4 inches, up to 8 to 10 inch diameter)
  4. May be difficult to differentiate from a secondary infection
  5. Risk of future systemic reaction: 5 to 10%

VII. Signs: Systemic Reaction

  1. See Allergic Reaction
  2. See Anaphylaxis
  3. Systemic Reaction or Anaphylaxis (responsible for 17% of all anaphylactic reactions)
    1. See Anaphylaxis for management
    2. IgE mediated reaction with Angioedema, Urticaria, respiratory distress
    3. Onset of reaction within 20 minutes of sting
  4. Delayed Hypersensitivity
    1. Reactions include Serum Sickness, Vasculitis, Glomerulonephritis, cerebral edema, DIC, Arthritis
    2. Rare complication of Insect Bite
    3. Occurs 3-14 days after large dose of venom
    4. Arthralgia and fever
  5. Massive Envenomation
    1. Rhabdomyolysis
    2. Multiorgan failure (renal, hepatic)
    3. Hemolysis
    4. Seizures
    5. Pancreatitis

VIII. Complications (rare - case reports)

IX. Differential Diagnosis

X. Management: Reaction

  1. General measures
    1. Remove Stingers still embedded in skin
      1. Avoids further Envenomation (esp. honeybee, bumblebee) and foreign body reaction
      2. Use a card or dull blade to scrape over the sting site (parallel to Stinger) to dislodge the Stinger
      3. Avoid squeezing the Stinger with forceps (injects more venom)
    2. Tetanus Vaccination is not needed for Hymenoptera Stings
  2. Systemic Allergic Reaction or Anaphylaxis Management
    1. See Anaphylaxis for management
    2. See Allergic Reaction
    3. Epinephrine 0.01 mg/kg (of 1 mg/ml solution) up to 0.3 mg in children and 0.5 mg in adults
    4. Other Anaphylaxis management includes ABC Management, Bronchodilators, Antihistamines, Intravenous Fluid
    5. BIphasic Reaction (uncommon)
      1. Mild to severe Anaphylaxis reccurs within 72 hours of initial reaction
      2. More likely in those requiring more than one dose of Epinephrine
        1. Observe for 6 to 24 hours
    6. Recurrent systemic reaction in 50% of cases from future Hymenoptera Sting
      1. Reaction is specific to the 3 types: Bees, Fire Ants or Vespidae (wasps, hornets, yellow jackets)
      2. Prescribe Epinephrine Autoinjector for those with anaphylactic reaction
      3. Systemic reaction risk is reduced to 3% risk with Desensitization
      4. Severe reaction is highest risk in small children, elderly or multiple stings
  3. Local Reaction
    1. Ice Packs or cool compresses
    2. Analgesics (e.g. NSAIDs, Acetaminophen)
    3. Unproven efficacy of other agents
      1. Antihistamines (e.g. Zyrtec)
      2. Topical Corticosteroids
      3. Topical papain (meat tenderizer) or Baking Soda
  4. Large Local Reaction
    1. Differentiate from Cellulitis and other vector borne conditions (e.g. Erythema Migrans)
    2. Prednisone or Methylprednisolone 1 to 2 mg/kg (children) up to 40 to 60 mg (adults) for 3 o 5 days
  5. Massive Envenomation (e.g. >100 stings)
    1. Results in direct venom toxicity
    2. Risk of cardiovascular collapse, Rhabdomyolysis, multisystem organ failure
    3. ABC Management and other supportive care
  6. Delayed Hypersensitivity or Serum Sickness
    1. Supportive care
    2. Systemic Corticosteroids
    3. Antihistamines

XI. Prevention

  1. See Stinging Insect Immunotherapy
  2. General
    1. Avoid floral print clothing
    2. Avoid floral fragrances
    3. Avoid walking barefoot
    4. Remove wasp and hornet nests when identified
    5. Cleanse outdoor garbage cans
    6. Clean eating areas of food remains
    7. Close food sources
  3. Bees
    1. Avoid walking through flowers
    2. Avoid bananas around hives (similar scent to bee alarm pheromone)
    3. Carbon dioxide and human sweat can also Antagonize bees
  4. Fire Ants
    1. Inspect playgrounds and yards for ant mounds
    2. Toxic bait may target queen ant

XII. References

  1. Cowling and Ferreri (2019) Crit Dec Emerg Med 33(2): 17-25
  2. Cowling and Lowes (2024) Crit Dec Emerg Med 38(1): 4-13
  3. Herness (2022) Am Fam Physician 106(2): 137-47 [PubMed]
  4. Kemp (1998) J Postgrad Med 103(6):88-106 [PubMed]

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