What is the recommended prophylaxis after an insect bite in a patient with a history of an allergic reaction (Hypersensitivity reaction)?

From the Guidelines

For individuals with a history of allergic reactions to insect bites, the recommended prophylaxis includes carrying an epinephrine auto-injector at all times, which should be administered immediately if severe allergic symptoms develop, as well as considering venom immunotherapy for long-term prevention. The standard adult dose of epinephrine is 0.3mg intramuscularly in the outer thigh, while children typically receive 0.15mg 1. Additionally, oral antihistamines like cetirizine (10mg daily), loratadine (10mg daily), or diphenhydramine (25-50mg every 4-6 hours) can be taken preventively before potential exposure to insects.

Key Recommendations

• Carrying epinephrine for emergency self-treatment and being familiar with proper use and indications is crucial 1
• Undergoing specific IgE testing for stinging insect sensitivity and considering immunotherapy is highly recommended 1
• Prevention strategies such as wearing long-sleeved clothing and pants when outdoors, avoiding bright colors and floral patterns, minimizing use of scented products, and staying away from areas where stinging insects gather are equally important

Venom Immunotherapy

Venom immunotherapy is highly effective in reducing the risk of a subsequent systemic reaction from an insect sting to less than 5%, and sting reactions that occur during immunotherapy are usually milder than those experienced before immunotherapy 1. The duration of immunotherapy is typically 3-5 years, but some experts recommend an extended duration, possibly indefinitely, in patients with a history of severe anaphylaxis 1.

Patient Education

Patients and caregivers of children who have experienced a systemic reaction to an insect sting should be taught how to administer epinephrine and under what circumstances to do so 1. Consideration of obtaining and carrying a medical identification bracelet or necklace is also recommended 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 recommended prophylaxis after an insect bite in a patient with a history of an allergic reaction (Hypersensitivity reaction) is not explicitly stated in the label.

• Key points:
  • The label discusses emergency treatment of allergic reactions, including anaphylaxis.
  • It does not provide information on prophylaxis after an insect bite. 2

From the Research

Prophylaxis after an Insect Bite in Patients with a History of Allergic Reaction

• The recommended prophylaxis after an insect bite in a patient with a history of an allergic reaction (Hypersensitivity reaction) includes measures to prevent future stings and allergic reactions 3, 4, 5, 6, 7.
• Patients with a history of severe systemic reactions, positive skin tests, and high levels of specific IgE antibodies may benefit from hyposensitization or venom immunotherapy (VIT) 3, 4, 6.
• VIT has been shown to be highly effective in reducing systemic reactions and anaphylaxis in patients with insect sting allergy 4, 6.
• Patients with a history of allergic reactions should be taught about prophylactic measures, such as avoiding areas where insects are common, wearing protective clothing, and using insect repellents 5.
• Self-injectable epinephrine and emergency preparedness are also crucial for patients with a history of severe allergic reactions 4, 5, 7.

Management of Allergic Reactions

• Local reactions can be treated with cold compresses, topical corticosteroids, and oral antihistamines 3.
• Mild systemic reactions can be treated with oral and intramuscular antihistamines and corticosteroids, while severe reactions require epinephrine injections 3, 4.
• Anaphylaxis requires immediate treatment with epinephrine and transportation to the emergency department for further evaluation 4, 7.