From the Guidelines
Insect sting reactions can be categorized as local, large local, or systemic (anaphylaxis), each requiring different management approaches. Local reactions involve pain, redness, and swelling limited to the sting site, typically lasting hours to a day. Treatment includes removing the stinger (if present), washing the area with soap and water, applying ice to reduce swelling, and using over-the-counter medications like acetaminophen or ibuprofen for pain and an antihistamine such as diphenhydramine (25-50mg every 6 hours) for itching, as suggested by 1.
Some key features of each reaction type include:
- Local reactions: pain, redness, swelling, and itching at the sting site, typically resolving within a day
- Large local reactions: extension of symptoms beyond the sting site, potentially affecting an entire limb, and persisting for several days, with management including elevation of the affected limb and possibly oral corticosteroids like prednisone (40-60mg daily for 3-5 days) for significant swelling, as noted in 1
- Systemic reactions (anaphylaxis): medical emergencies with symptoms beyond the sting site, including hives, swelling of lips/tongue/throat, difficulty breathing, dizziness, nausea, or hypotension, requiring immediate epinephrine administration (0.3mg for adults, 0.15mg for children, via auto-injector into the outer thigh) and emergency services, as emphasized in 1
Immediate treatment for systemic reactions requires epinephrine administration, calling emergency services, and supplemental treatments at a medical facility, including antihistamines, corticosteroids, and bronchodilators, with anyone having a history of systemic reactions advised to carry epinephrine auto-injectors, consider immunotherapy, and wear medical identification, as recommended in 1 and 1.
It's crucial to differentiate between these reaction types to provide appropriate management and prevent potential complications, especially in cases of systemic reactions where delayed epinephrine administration can be fatal, as highlighted in 1.
From the FDA Drug Label
1 INDICATIONS & USAGE Adrenalin® is available as a single-use 1 mL vial and a multiple-use 30 mL vial for intramuscular and subcutaneous use. Emergency treatment of allergic reactions (Type I), including anaphylaxis, which may result from allergic reactions to insect stings, biting insects, foods, drugs, sera, diagnostic testing substances and other allergens, as well as idiopathic anaphylaxis or exercise-induced anaphylaxis. The signs and symptoms associated with anaphylaxis include flushing, apprehension, syncope, tachycardia, thready or unobtainable pulse associated with hypotension, convulsions, vomiting, diarrhea and abdominal cramps, involuntary voiding, airway swelling, laryngospasm, bronchospasm, pruritus, urticaria or angioedema, swelling of the eyelids, lips, and tongue.
- Anaphylaxis (Systemic Reaction):
- Features: flushing, apprehension, syncope, tachycardia, thready or unobtainable pulse associated with hypotension, convulsions, vomiting, diarrhea and abdominal cramps, involuntary voiding, airway swelling, laryngospasm, bronchospasm, pruritus, urticaria or angioedema, swelling of the eyelids, lips, and tongue
- Treatment: epinephrine (IM) for emergency treatment of anaphylaxis
- Local and Large Local Reactions: The FDA drug label does not provide information on the features and treatment of local and large local reactions. 2
From the Research
Insect Sting Reaction Types
Insect sting reactions can be categorized into three main types: local, large local, and systemic (anaphylaxis). The features and treatment for each type are as follows:
- Local Reaction
- Characterized by redness, swelling, and pain at the site of the sting
- Typically resolves on its own within a few hours
- Treatment is symptomatic, with measures such as applying a cold compress, elevating the affected area, and taking oral antihistamines or pain relievers as needed 3
- Large Local Reaction
- Similar to a local reaction, but with more pronounced symptoms and a larger area of involvement
- May take several days to resolve
- Treatment is also symptomatic, with measures such as applying a cold compress, elevating the affected area, and taking oral antihistamines or pain relievers as needed 3
- Occurs in up to 25% of the population, but is rarely dangerous 3
- Systemic Reaction (Anaphylaxis)
- A life-threatening, IgE-mediated reaction that can occur within minutes to hours after a sting
- Characterized by symptoms such as urticaria, difficulty breathing, and mucosal swelling
- Requires immediate treatment with intramuscular epinephrine, followed by supportive care and observation for potential biphasic reactions 4, 5
- Can be fatal if not treated promptly and properly
- Venom immunotherapy is 75% to 98% effective in preventing sting anaphylaxis and can be stopped after 5 years in most cases 6, 7, 5
Risk Factors and Prevention
Certain individuals are at higher risk for developing a systemic reaction to an insect sting, including those with a history of anaphylaxis, mastocytosis, or other underlying medical conditions 3, 4. Prevention measures include avoiding areas where stinging insects are common, wearing protective clothing, and carrying an epinephrine auto-injector if prescribed by a healthcare provider. Venom immunotherapy is also an effective long-term management strategy for individuals with a history of anaphylaxis 6, 7, 5.