Week 7 ~ Insect Sting Allergies

Hymenoptera venom allergy is simply an allergy to an insect sting. But to be more specific, it is "an immunoglobulin E (IgE)- mediated hypersensitivity to the venom of insects in the insect order Hymenoptera" (Paschall, 2014). I have always been interested in how some people don't have much of a reaction at all to a bee sting, while others could die without being treated. I don't know too much about this, though, so I thought it would be a good topic to research, especially why the allergy usually doesn't manifest until after the first couple stings. I have never been stung before, but for some reason I am not a big fan of bees, wasps, yellow jackets, etc. Whenever I happen to encounter one, I tend to overreact more than the average person probably does :) When I was younger I was always afraid of being allergic to them. My good childhood friend was very allergic to bees, so that is what probably caused me to be more paranoid about it.

Being stung by one of the insects in the order Hymenoptera can lead to systemic reactions. These types of reactions cause signs and symptoms throughout the body, some only mild while others life threatening. Mild systemic reactions may include flushing of the skin, uticaria (hives), and angioedema (swelling under the skin). More severe, or life-threatening, systemic reactions (also known as anaphylaxis) can include bronchospasm (a sudden constriction of the muscles in the walls of the bronchioles), laryngeal edema (a swelling caused by fluid accumulation in the soft tissues of the larynx), and hypotension. As stated in one source, "Venom-induced anaphylaxis can be particularly severe and is a leading cause of fatal anaphylaxis" (Tracy, 2013).

An insect sting allergy can develop at any age. Systemic reactions to Hymenoptera venom occur in about 3% of adults and in only about 1% of children younger than 17 years, which is interesting because children are stung more often than adults. Many of the reactions that children have are just mild, and large local reactions to stings are also more common in children (incidence of 20% for children and 10% for adults). The prevalence of insect sting allergy is twice as high in males as in females. This may be due to environmental factors such as increased exposure rather than genetic factors like inherent susceptibility. According to an online article from the Cleveland Clinic (2014), "There is no clear association with other allergies, and only 30% of patients with venom allergy are atopic. In addition, insect sting allergy is statistically not more likely to occur in persons with a family history of sting reactions." I found this last piece of information pretty interesting because I assumed it could be inherited.

In the United States, there are at least 50 deaths per year caused by insect sting reactions, and about one half of these deaths occur in victims with no prior history of a sting reaction. This number may be pretty large due to the fact that these people probably aren't as prepared to deal with the reaction since they have never experienced one before. Another interesting fact is that most fatalities (80%) occur in adults older than 40, and just 2% of fatalities occur in individuals younger than 20 years (Paschall, 2014). Perhaps the sting reactions grow worse over time or the body starts to become more sensitive to the venom as it ages. Another reason for this could be because older adults have obviously been alive longer, giving them more opportunities to have been stung more than once: "At least one prior sting is required to sensitize a person to venom, and sensitization is more likely to occur following multiple simultaneous stings or subsequent stings occurring over a relatively short period of time" (Paschall, 2014). Since an older person has been alive longer than a younger person, the older person is more likely to have had more sting reactions throughout his/her life compared to a child. The more severe reactions that one experiences, the higher his/her chance of fatality becomes.

It is crazy how the little stinger of a bee has the potential to cause such severe reactions in a person's body. The body is just trying to protect itself from the venom, but the immune system ends up overreacting and doing more harm than good. Thankfully these life-threatening systemic reactions are not common, but they are possible and do occur. As stated above, the two main risk factors for developing an insect sting allergy are 1) having multiple stings at one time and 2) being stung sequentially at close intervals. These two factors relate to an individual's environment, lifestyle, etc. rather than his/her biology such as the immune system. I was having trouble, though, finding more biology-related risk factors. For example, not everyone who experiences multiple stings at once ends up developing an allergy. So what makes them different from those who do develop the allergy?



References
1. Paschall, V. L. (2014). Hymenoptera venom allergy. Cleveland Clinic. Retrieved from http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/allergy/hymenoptera-venom-allergy/
2. Tracy, J. M. (2013). Diagnosis of hymenoptera venom allergy. UpToDate. Retrieved from http://www.uptodate.com/contents/diagnosis-of-hymenoptera-venom-allergy
3. Photo (top): http://bee-stings.net/bee_stinger2.jpg
4. Photo (middle): http://pics.davesgarden.com/pics/2006/08/29/mygardens/40fec6.jpg
5. Photo (bottom): http://justoutsidetheboxcartoon.files.wordpress.com/2012/04/img_0605.jpg