Article from August, 2016

Dealing with Insect Stings

insect stings

by Michael J. Manyak, MD, MED 92

Most organisms become more active with warm weather.  But along with the beauties of nature come some very necessary creatures which cause occasional consequences for humans.  The sometimes disproportionate fear of certain insects is well ingrained in our psyche.  Unfortunately for some, bee and wasp stings pose a real threat to health beyond temporary discomfort.  The Burmese proverb to beware of a man’s shadow and a bee’s sting is certainly prescient for the travelers with allergies to these insects.

Stings from insects belonging to the insect order Hymenoptera are among the most important causes of systemic allergic reactions.  The likely culprits come from 3 families within this order which are the honeybees and bumblebees, the hornets, wasps, and yellow jackets, and fire ants.  The venoms from these 3 families are different so there is little cross-reactivity among them.  Therefore, an allergy to bees does not mean there will be an allergic reaction to a wasp sting.  However, within families, there can be significant cross-reactivity, such as with hornets, wasps, and yellow jackets.  In those cases, an allergy to one can precipitate an allergic reaction from a related insect sting.  Honeybee and bumblebee allergies are distinct.

Only females can sting because the stinger is actually a modified egg-laying organ no longer used for that purpose.  Most insects sting to defend themselves and nests. Hymenoptera insect groups inject different amounts and types of venom.  All stings contain venom with vasoactive substances that cause pain, itching, and swelling at the site of the sting.  Fire ant venom, for example, contains small amounts of proteins but substantial amounts of toxic alkaloids, which are responsible for the characteristic vesicles seen after their bites.  Protein enzymes in the venom are the cause of systemic symptoms in those allergic.  Patients susceptible to allergic reactions are sensitized by a sting or bite that may not elicit an allergic response but any subsequent stings starts the allergic response.  In these sensitized patients, the chain reaction of the immune system can cause a wide spectrum of reactions ranging from local reactions to itching and cardiovascular collapse known as anaphylaxis.  Less than 10% of patients with a large local reaction have systemic reactions to subsequent stings.  However a previous systemic reaction correlates with high risk of a subsequent systemic reaction.

Severe systemic allergic reactions occur in less than 1 percent of children and about 3 percent of adults.  Anaphylaxis from bee and wasp stings causes at least 40 deaths per year in the US and is likely underestimated.  Honeybees are less aggressive but their sting is more likely to lead to systemic reaction.  Africanized honeybees are more aggressive but their venom is no more toxic than other honeybees though with multiple stings from an aggressive swarm, life-threatening reactions may result.  Bee stings are also a source of rare neurological disorders and kidney failure from delayed reactions.

TREATMENT

LOCAL REACTIONS

  • Most stings cause acute pain and transient localized swelling.
  • Treat with ice, pain meds, oral anti-histamines, topical steroid creams to reduce itching, swelling, and pain.
  • Scrape the skin with your fingernail or credit card to remove retained stingers from honeybees. Bumblebees do not leave stingers behind.  The stinger will likely be emptied of venom after 30 seconds with no consequence if not removed.
  • Large local reactions of the tongue or mouth may compromise the airway and oral steroids, if available, may be useful. Seek medical attention if this occurs.
  • Infections of sting sites are very rare so antibiotics are not given.
  • Fire ants typically have pustules 1 to 2 days after stinging which should be kept intact and cleaned to avoid secondary infection.

SYSTEMIC REACTIONS

  • Severe systemic reactions usually occur rapidly after a sting but may be delayed or followed by a recurrence typically within 8 hours. Less than 20% of people with allergic reactions have a recurrence.
  • At the first sign of severe allergic reaction, inject epinephrine (prepared dose known as Epi-pen, Auvi-Q, or Adrenaclick) into the thigh
  • Delayed injection of epinephrine is associated with more severe reactions.
  • Repeat injection of epinephrine at 5 to 15 minute intervals if the patient has persistent symptoms or a recurrence of symptoms. Most patients require only one or two doses.
  • There are no contraindications for epinephrine use for anaphylaxis treatment including cardiovascular disease or high blood pressure.

LONG TERM THERAPY for those with a SYSTEMIC ALLERGIC RESPONSE

  • Avoid exposure. Wear long sleeves and pants, and obviously avoid activities where exposure may occur.
  • Carry an epinephrine auto-injector and get a prescription for more in case of a recurrent episode.
  • Make an appointment with an allergist/immunologist to be tested for specific venom sensitivity and consider longer term immunotherapy if identified. Trials of subcutaneous immunotherapy have shown a significant reduction, to less than 5%, in the risk of a subsequent systemic reaction to an insect sting.

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This article was published in The Explorers Journal

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