Insect Stings and Bites Dissected: Part 1

When you are out in nature, trying to enjoy a peaceful time by yourself, there is hardly anything more annoying than those buzzing pests that are constantly trying to (or seemingly trying to) get a piece of you or leave a piece of them in you.  Most of the time these little critters can be little more than a pain in the neck and inconvenience, but sometimes they can be more.  When can we just ignore the pain and move on, and when should we do more?Bee

Hymenoptera (Bees, Wasps and Ants)

These are an important group of venomous insects due to their abundance and the potential complications of their envenomation.  In particular, over 350 fatal attacks by bees have been recorded, with over 190 having occurred in Mexico and future estimates in the area being 60 deaths a year.1  In the US there are already over 40 deaths a year from anaphylaxix due to hymenoptera stings.2  The most well-known cause is anaphylaxis, however to a non-allergic person the number of stings required from a honeybee to inflict death is estimated from 500-1500.1

WaspSingle stings from a hymanoptera species to an unsensitized person causes pain, wheal formation and potentially some edema.1  It can also cause lymphangitic streaks within 1-2 days, which should not be mistaken for cellulitis.  Large local reactions are genearlly not dangerous as long as they do not occur on the face or near the airway.  These reactions are due to the local release of vasoactive amines including histamine and dopamine, along with norephinephrine and kinins.  Fire ant bites additionally can result in the formation of a vesicle that turns into a sterile pustule.  Multiple bites or stings can lead to more serious symptoms such as diarrhea, vomiting, dyspnea, tachycardia, hypotension or collapse.   Rare instances of renal failure, hemolytic anemia, encephalitis, myocarditis, Guillain-Barre syndrome and acute pancreatitis have also been documented.1, In the case of a sting, it is important to first remove the stinger as the venom sac can continue to pump venom.

Fire ant

It is better to remove it quick than taking time to look for a knife or a credit card to scrape it off…time is of the essence and the notion that you will worsen the injury by squeezing in additional venom has been discredited.1,3   For the non-allergic stings, apply ice or a cold pack, take Benadryl (25-50mg every 4 hours) and Ibuprofen or Acetaminophen to help alleviate swelling and pain.  For bee stings, application a past of baking soda and water has been suggested, but not supported.  This is likewise for application of an acidic substance (e.g. vinegar, lemon juice) to wasp stings.3  Topical “sting sticks” and topical aspirin paste are also not effective.  Meat tenderizer applied to the sites does however seem to be of value in helping to denature the venom and reduce pain.3  Topical antihistamines or steroids  may help, and oral steroids can help resolve extensive local reactions (important to give for large local reactions near airway to prevent compromise).1,

 

Tylenol

For anaphylaxis, inject epinephrine using an EpiPen in the anterolateral aspect of the thigh.  Of note, EpiPens expire every 1-1.5 years, and a study done in rabbits previously found that expired epinephrine had significantly reduced bioavailability proportional to the number of months past due it was.4  However, if an expired EpiPen is all that is available it should be given as long as it is not discolored and there are no precipitates visible.4  If taking it along on a hike, it should remain at a temperature between 59°F – 86° F, which means if you are out on a cold hike it should be kept within your insulating layer and close to your body heat.   One thing to keep in mind following Epinephrine injection is that in some people it may aggravate heart conditions and can lead to ventricular arrythmias.  Having a heart condition is not a contraindication to receiving epinephrine, and a person in anaphylaxis should never have it withheld because of this.1

References

  1. Auerbach, Paul S. “Chapter 50: Arthropod Envenomation and Parasitism.” Wilderness Medicine. 6th ed. Philadelphia, PA: Elsevier/Mosby, 2012. Print.
  2. Casale, TB and Burks AW.  “Hymenoptera-Sting Hypersensitivity.”  NEJM 2014; 370: 1432-1439.
  3. Weiss, Eric A. “Insect Bites and Stings.” A Comprehensive Guide to Wilderness and Travel Medicine. Oakland, CA: Adventure Medical Kits, 1997. 121-28. Print.
  4. Estelle F, Simons R, Gu X, Simons KJ. Outdated EpiPen and EpiPen Jr autoinjectors: Past their prime? J Allergy Clin Immunol 2000;1025-1030.