May 2018

Wasp stings: Some really do hurt more than others, and how to counsel patients

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As summer approaches and we become more active outdoors, wasps will become more active, too. Two recent studies highlight the pain and danger of the ubiquitous wasp.

The first study, from entomologists at the University of Utah, looked at stinger length compared to reported pain and toxicity.1 Pain from the wasp sting comes from 2 sources: venom (typically measured by LD50, a measure of lethality) and puncture wound. Wasp venom, they report, varies in toxicity from 0.25 mg/kg to 71 mg/kg, depending on the species. The venom, which can be alkaloid or proteinaceous, is a chemical cocktail that breaks down cell membranes, constricts blood vessels to reduce blood flow and increase blood pressure, and stimulates pain nerves as well as the histamine response.

As for the second cause of pain—the mechanical damage caused by the stinger—researchers found a significant positive relationship between the mesosomal, or midbody, length and stinger length (P<.0001), and between overall stinger length and pain (P<.001), which is consistent with other reports that larger wasps do indeed produce a more painful sting. Interestingly, there was no significant relationship between venom lethality and pain.

The second study,2 from Stanford University’s Department of Surgery, reviewed mortality data from the US Centers for Disease Control and Prevention related to nonvenomous and venomous animals for 2008 through 2015. While most deaths were related to injury caused by larger animals (e.g., horses, cows), nearly 30% were caused by stings from wasps, hornets, and bees—numbers that have been consistent for the past 20 years.

  • Wasps can sting more than once.
  • There are 800+ species of social wasps who
    create nests.
  • Wasps beat their wings 117 to 247 beats per second, depending on their size.
  • For more detailed information about stings of all types, search on the Internet for “Schmidt Pain Index,” which is how one entomologist assessed and compared the pain of more than 30 different insect stings he experienced during his work.

For the average patient presenting in the office, swelling and pain caused by a wasp sting should peak at 48 hours, but may continue for a week and affect the entire limb. Clinical evaluation should include checking for the stinger and removing it, and assessing upper and lower airways.3 Suggested treatments for pain, burning, and itching include ice, an antihistamine, and a nonsteroidal anti-inflammatory drug. Patients  with a known allergic reactivity to insect sting  should be encouraged to carry a syringe prefilled with epinephrine.

If swelling and erythema begin 24 to 48 hours after the sting, pain is increasing, and there are other signs of systemic infection (e.g., chills and fever), however, consider the rare case of secondary bacterial cellulitis.3

Sources:

  1. Sadler EA, Pitts JP, Wilson JS. Stinging wasps (Hymenoptera: Aculeata), which species have the longest sting? PeerJ. 2018;6:e4743.
  2. Forrester JA, Weiser TG Forrester JD. An update on fatalities due to venomous and nonvenomous animals in the United States (2008-2015). Wilderness Environ Med. 2018;29(1):36-44.
  3. Barish RA, Arnold T. Insect stings. In: Merck Manual: Professional Version. Kenilworth, NJ: Merck Sharp & Dohme Corp. 2018. www.merckmanuals.com/professional/injuries-poisoning/bites-and-stings/insect-stings. Accessed June 20, 2018.
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