SELECTED ARTICLES FROM THE RECENT LITERATURE 2005

12/8/05

Prevention and treatment of insect sting reactions

Summary
Background - Policies concerning the prevention and treatment of hymenoptera insect sting reactions (ISR) have evolved somewhat in recent years.

Findings - Guidelines in this area have been formulated recently by the Interest Group on Insect Venom Hypersensitivity of the European Academy of Allergy and Clinical Immunology. Patients with previous systemic ISR should be referred to an allergist (if not already followed by one) for evaluation and venom allergen immunotherapy (VIT) if indicated. VIT has been shown conclusively to prevent severe systemic ISR. An emergency medical kit should be provided to all such patients. IM injection of epinephrine is the treatment of choice for systemic ISR with multiple organ system involvement. Mild to moderate reactions involving only the skin may be controlled by just antihistamines w/wo systemic corticosteroids.

Several approaches can be considered in deciding whether to discontinue VIT:

1) If the venom skin tests and in vitro IgE anti-venom antibody tests become negative after 3 years of VIT, this treatment can be discontinued; 2) even if the venom skin tests are persistently positive after 5 years of VIT, one can consider stopping VIT if the previous ISR was mild-moderate (no hypotension, cardiac effects, severe asthma, upper airway obstruction); 3) if the previous ISR was severe, continue the VIT indefinitely.

Reference
Allergy 2005;60:1459-70

Editor's Comments
I think that these guidelines are quite reasonable. However, I would feel somewhat uneasy treating a prominent generalized urticarial ISR without other organ involvement with just antihistamines. Occasionally, such ISR apparently limited to the skin may rapidly involve other organ systems. The only antihistamine used parenterally for allergic reactions is diphenhydramine. Oral forms of antihistamines may not work fast enough particularly when given shortly after eating. Corticosteroids likely work too late to control potentially life-threatening early manifestations of ISR, even when given IV.

The recommendations concerning stopping VIT are in line with those made previously by the Hopkins group. However, more recent data suggest that gradual loss of tolerance of insect stings may occur several years after stopping VIT. Also, negative venom skin test responses usually, but not always, indicates that an ISR will not occur with a subsequent sting.

 

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