Whether it is a runny nose, itchy eyes, or a skin rash, many of us have faced the systems of an allergic reaction at some point in our lives. They are a determining factor in the places we go, the pets we have, and even the food we eat. The Asthma and Allergy Foundation estimates that allergies affect 50 million Americans, making it the fifth leading chronic disease in the country. Despite the frequency of allergies in the population, few individuals really understand how allergies occur (1).
A healthy body’s immune system is set up to constantly identify invading pathogens by identification of self vs. non-self. While one definitely should not be upset that the body has this skill, things can become problematic when the body cannot differentiate what non-self entities are harmful or harmless. Allergies are induced when the body begins to strike against non-harmful entities (5).
When an allergy is induced, the body identifies an allergen, inducer of the allergic response, as an invader. An allergen may be anything individuals are exposed to in day to day life (2). In order to remove this invader, the body elicits a response to destroy it. T-cells and B-cells, two types of White Blood Cells, play an important role in eliciting this response. When these cells are presented with a foreign substance, T-cells either recruit more White Blood Cells or directly attack whatever invader is present. B-cells release antibodies, which are also engineered to fight off the specific invader. IgE is the antibody specifically associated with allergic reactions. It bonds to basophils and mast cells, eventually causing them to release their contents, including a protein named histamine (5).
Histamine influences the body by causing inflammation. When an area of the body is inflamed, blood vessels become less dense, allowing an increase in the number of blood cells able to enter the site of histamine release. This increase in blood cells causes swelling at the site of the allergic reaction (4). These additional blood cells may also trigger the allergic response, causing the reaction to become worse with continued exposure. Histamine also causes smooth muscle to contract (6), which leads to breathing difficulties frequently associated with an allergic reaction.
There are several ways a person may try to deal with allergies. Some simply try to avoid allergens that tend to cause an immune response. Sometimes, allergens cannot be avoided, so allergy treatment drugs are provided. One common way to treat allergies is to use anti-histamines, such as Claritin and Allegra. They work to inhibit the ability of histamine to bond with other molecules that cause the allergic response (4). In severe allergic reactions, some individuals require an epinephrine injection. Epinephrine causes blood vessels to contract, inhibiting the allergic response (3). In severe cases, immunotherapy may be used. Immunotherapy forces the patient to be exposed to the allergen that normally elicits a response. While it is not always effective, in some cases it causes the body to release IgG, a blocking antibody that improves a subject’s response to an allergen (5).
While some of these ways of dealing with allergies are achieving a reasonable amount of success with sufferers, a larger question remains. How do we prevent allergies from developing in the first place? Research from the University of Copenhagen claims allergies tend to develop more prevalently in individuals who are not exposed to many types of bacteria in the first six months of life (7). This is why infants born via cesarean section have a much higher tendency to develop allergies than those born naturally (7). Naturally born children are much more heavily exposed to the mother’s bacteria in the birthing process. Some researchers suggest this reasoning is also why children raised in rural environments are less prone to develop allergies.
Though we still have a lot that we may learn about allergies, the information we see indicates that an increase in allergies is being caused by modern medicine. By not allowing bacterial exposure early in life, we are forced to face alternate medical consequences. Hopefully, researchers will develop a fuller idea of how to prevent both illness and allergies, but, in the meantime, we are left to take our Claritin, fear our bees, and exhibit caution in the presence of peanuts.
1. “Allergies – PubMed Health.” Web. 09 Nov. 2011. <http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001815/>.
2. Cunha, John P. “Allergic Reaction Symptoms, Causes, Signs, Treatment and Prevention by EMedicineHealth.com.” EMedicine Health. Web. 09 Nov. 2011. <http://www.emedicinehealth.com/allergic_reaction/article_em.htm>.
3. “Epinephrine Injection: MedlinePlus Drug Information.” National Library of Medicine – National Institutes of Health. Web. 09 Nov. 2011. <http://www.nlm.nih.gov/medlineplus/druginfo/meds/a603002.html>.
4. “Histamine.” Biology @ Davidson. Web. 09 Nov. 2011. <http://www.bio.davidson.edu/courses/immunology/Students/spring2000/lamar/mfirp.htm>.
5. “HowStuffWorks “How Allergies Work”” HowStuffWorks “Science” Web. 09 Nov. 2011. <http://science.howstuffworks.com/environmental/life/human-biology/allergy.htm>.
6. Schmidt D, Ruehlmann E, Branscheid D, Magnussen H, Rabe KF. 1999 Aug. Passive sensitization of human airways increases responsiveness to leukotriene C4. European Respiratory Journal 14(2): 315-319.
7. Hans Bisgaard, Nan Li, Klaus Bonnelykke, Bo Lund Krogsgaard Chawes, Thomas Skov, Georg Paludan-Müller, Jakob Stokholm, Birgitte Smith, Karen Angeliki Krogfelt. 2011. Reduced diversity of the intestinal microbiota during infancy is associated with increased risk of allergic disease at school age. Journal of Allergy and Clinical Immunology 128 (3): 646 -652.