The Exchange

Commentary and Observations from
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Stinging Insect Allergy

Stinging Insect Allergy

Stinging insect allergy accounts for 10% of all cases of anaphylaxis. Stings from flying hymenopterans and fire ants are responsible for most cases. Approximately 0.8% of children and 3.5% of adults experience systemic reactions to some type of stinging insect in their lives, and in the US alone, at least 40 deaths per year are attributed to insect allergy.

The most common stinging insects that cause allergic reactions include the Apidae (honeybee, bumblebee), Vespidae (yellow jacket, yellow hornet, white-faced hornet), Polistinae (paper wasp), and Formicidae (fire ant). Venom from insects of the order Hymenoptera, such as honeybees, wasps, and yellow jackets, contains various proteins and enzymes that trigger allergic reactions; the venom in fire ants contain proteins and alkaloids. However, there can be cross-reactivity between venoms in each family.

The clinical history is the most important component in evaluating patients with stinging insect allergy. Biting insects such as mosquitos can cause local allergic reactions involving a large, indurated, erythematous lesion at the site (referred to as Skeeter Syndrome). Anaphylaxis is rarely seen with biting insects. Stinging insects can also cause local reactions, which can be more concerning as they can be larger and cross joint lines. Local reactions are associated with later systemic reactions in 5% to 10% of patients. Systemic reactions involve symptoms distal to the sting site and involve multiple body systems. Symptoms include urticaria, angioedema, conjunctivitis, rhinitis, laryngeal edema, bronchospasm, shortness of breath, nausea, vomiting, diarrhea, abdominal pain, arrhythmia, hypotension, and syncope. It is important for the clinician to inquire about each body system, as failure to identify a systemic reaction can have potentially life-threatening complications for that patient in the future.

Patients suspected of having anaphylactic or systemic reactions should be referred to an allergist. Skin testing (often called "venom challenge" or "insect challenge") should be completed. If skin testing is negative, serologic testing may also be performed. The accuracy of clinical testing is limited. Patients should be prescribed an epinephrine auto-injector and educated on proper use, identification of future systemic reactions, and insect avoidance measures.

Venom immunotherapy (VIT) is recommended for all patients with history of systemic reaction to stinging insects. VIT has been shown to be extremely effective at reducing the severity of future reactions. Patients generally receive VIT to all venoms that they tested positive to, regardless of any patient-reported history of reacting to "all" insects. It is important to note that many patients falsely identify insects when providing their clinical history. Patients "build up" on their VIT, starting at a miniscule dose, and continuing based on the dosing schedule decided between the patient and provider (ie, rush, modified rush, or conventional build-up).

Once a maintenance dose of VIT is reached, patients remain on monthly VIT for 3 to 5 years. If another systemic reaction occurs while on VIT, the maintenance dose can be increased. Systemic reactions to VIT can happen, and therefore VIT must only be provided in a healthcare setting equipped to manage anaphylactic reactions.

References
  • Tankersley MS, Ledford DK. Stinging insect allergy: State of the art 2015. J Allergy Clin Immunol Pract. 2015;3:315-322.

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Filed under: Allergy/Immunology

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