Allergies

The intense beauty of the idyllic autumn day always makes me feel privileged to live in a place that experiences the season to its full effect. 

The way the calm and glassy waters of the St. Lawrence River reflect the stunning colours of the sun streaked sky off its surface. With only the occasional autumn breeze to disturb its serenity, creating gentle ripples through its dark blue waters. 

The downy clouds with their swift motion creating a dizzy whirlwind of dancing leaves on the path in front of me as I walk through the forest, gazing admiringly at the autumnal landscape of brilliant orange, rusty yellow and fiery red leaves set alight by the bright, warm sun. 

The squirrels, red, grey and black, scurrying about with their acorns.

Smiling inwardly as I walk, breathing in the bitter sweet aroma of the tumbling leaves. Wondering if it is simply the rarity of such days that has earned them my admiration, or rather autumn’s ability to both liberate me from the stifling heat of summer and provide a brief reprieve before the damp, dark and depressing months of winter.

RAGWEED

And then I spot it, or rather my nose, skin and immune system spot it: my nemesis, one Ambrosia psilostachya, ragweed to you and me. And any pleasure I was deriving from my blissful walk ends abruptly in a tantrum of snot, hives and itchy red eyes.

So today, I thought I might attempt to learn a little more about the bane of my autumn existence, namely, allergies.

ALLERGIES

When normally harmless things like dust and pollen enter the body, the immune system of an allergic person recognizes them as allergens and experiences a hypersensitive immune response (allergic reaction), through the actions of the IgE antibody. [1][2]


Allergic individuals generally produce the IgE antibody in larger amounts than normal. [1]


When these IgE antibodies bind to the antigen (allergen), this leads to the release of various chemicals like histamines (from Mast cells), which in turn cause localized swelling, inflammation, itching, and mucus production. Once sensitized, the immune system is capable of mounting this exaggerated response with subsequent exposures to the allergen. [1]

TISSUES AFFECTED IN ALLERGIC INFLAMMATION
(Antibodies are synthesized by B-cells)

• Typically, there is a period of "sensitization" ranging from days to years prior to an allergic reaction. [1]

• Other antigens, such as bacteria, do not lead to production of IgE, and therefore do not cause allergic reactions. [1]

• Lactose intolerance, a common reaction to milk, is not a form of allergy at all, but rather due to the absence of an enzyme in the digestive tract. [2]

• Latex and banana sensitivity may cross-react. Furthermore, those with latex allergy may also have sensitivities to avocado, kiwifruit, and chestnut. [2][4]

• Allergic diseases are strongly familial: identical twins are likely to have the same allergic diseases about 70% of the time; the same allergy occurs about 40% of the time in non-identical twins. [2][5] 

• Allergic parents are more likely to have allergic children. [2][6]

• Some allergies, however, are not consistent along genealogies; parents who are allergic to peanuts may have children who are allergic to ragweed. [2]

• It seems that the likelihood of developing allergies is inherited and related to an irregularity in the immune system, but the specific allergen is not. [2][5]

• The prevalence of allergic conditions has increased significantly over the last two decades and continues to rise. [1]

• The ‘Hygiene hypothesis’ proposes that individuals living in too sterile an environment are not exposed to enough pathogens to keep the immune system busy. [7]

• Since our bodies evolved to deal with a certain level of such pathogens, when they are not exposed to this level, the immune system will attack harmless antigens and thus normally benign microbial objects — like pollen — will trigger an immune response. [2][8]

• A variation of the ‘Hygiene hypothesis’ suggests that co-evolution of man and parasites has led to an immune system that functions correctly only in the presence of the parasites. Without them, the immune system becomes unbalanced and oversensitive. [2][9][10]

• The use of antibiotics in the first year of life has been linked to asthma and other allergic diseases. [2][11]

• Children born via Cesarean section have a higher risk of allergy as compared to children who are delivered vaginally. [1][12]

• Exposure to tobacco smoke increases the risk of allergy. [1]

• Boys are more likely to be allergic than girls. [1]

• Allergy testing can help confirm or rule out allergies. [13][14] 

• To assess the presence of allergen-specific IgE antibodies, two different methods can be used: a skin prick test, or an allergy blood test. Both methods are recommended, and they have similar diagnostic value. [2][14][15]

• Allergies can not only develop at any age, but many individuals also outgrow allergies over time. [1]
• For example, peanut allergies can sometimes be outgrown by children. [2]

• Epinephrine auto-injectors, which are administered by injection to treat a life-threatening allergic reaction called anaphylactic shock contain adrenaline (epinephrine), a chemical naturally released by the body in times of stress. [16]

• Anaphylactic shock is a severe, potentially life-threatening allergic reaction that can be triggered just minutes following exposure in people with a severe allergy. The adrenaline rapidly reverses the symptoms of anaphylaxis by causing blood vessels narrow and redirecting blood to vital organs. [3]

UPDATES:

Dirty farm air may ward off asthma in children / newssciencemag.org / September 3, 2015

Why Do We Have Allergies/ Discover Magazine / April 7, 2015












REFERENCES

[1] http://www.medicinenet.com/allergy/article.htm
[2] http://en.wikipedia.org/wiki/Allergy
[3] http://www.netdoctor.co.uk/allergy-and-asthma/medicines/epipen.html
[4] Fernández de Corres L, Moneo I, Muñoz D, Bernaola G, Fernández E, Audicana M, Urrutia I (January 1993). "Sensitization from chestnuts and bananas in patients with urticaria and anaphylaxis from contact with latex". Ann Allergy 70 (1): 35–9. PMID 7678724.
[5] Galli SJ (2000). "Allergy". Curr. Biol. 10 (3): R93–5. doi:10.1016/S0960-9822(00)00322-5. PMID 10679332.
[6] De Swert LF (1999). "Risk factors for allergy". Eur. J. Pediatr. 158 (2): 89–94.doi:10.1007/s004310051024. PMID 10048601.
[7] "The Hygiene Hypothesis". Edward Willett. 2013-01-30.
[8] Yazdanbakhsh M, Kremsner PG, van Ree R (2002). "Allergy, parasites, and the hygiene hypothesis". Science 296 (5567): 490–4. doi:10.1126/science.296.5567.490. PMID 11964470.
[9] Gibson PG, Henry RL, Shah S, Powell H, Wang H (September 2003). "Migration to a western country increases asthma symptoms but not eosinophilic airway inflammation".Pediatr. Pulmonol. 36 (3): 209–15. doi:10.1002/ppul.10323. PMID 12910582.

[10] Addo-Yobo EO, Woodcock A, Allotey A, Baffoe-Bonnie B, Strachan D, Custovic A (February 2007). "Exercise-induced bronchospasm and atopy in Ghana: two surveys ten years apart". PLoS Med. 4 (2): e70. doi:10.1371/journal.pmed.0040070.PMC 1808098. PMID 17326711.
[11] Marra F, Lynd L, Coombes M, et al. (2006). "Does antibiotic exposure during infancy lead to development of asthma?: a systematic review and metaanalysis". Chest 129 (3): 610–8.doi:10.1378/chest.129.3.610. PMID 16537858.
[12] Thavagnanam S, Fleming J, Bromley A, Shields MD, Cardwell, CR (2007). "A meta-analysis of the association between Caesarean section and childhood asthma". Clin. And Exper. Allergy 38 (4): 629–33. doi:10.1111/j.1365-2222.2007.02780.x.PMID 18352976.
[13] NICE Diagnosis and assessment of food allergy in children and young people in primary care and community settings, 2011
[14] Boyce J et al.. Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of NIAID-Sponsored Expert Panel. J Allergy Clin Immunol 2010; 126: S1–S58
[15] Cox, L. Overview of Serological-Specific IgE Antibody Testing in Children. Pediatric Allergy and Immunology. 2011.
[16] http://en.wikipedia.org/wiki/Epinephrine_autoinjector

ADDITIONAL SOURCES

http://www.webmd.com/allergies/
http://en.wikipedia.org/wiki/Ragweed
http://www.ncbi.nlm.nih.gov/books/NBK26884/

IMAGE CREDITS


"Ambrosia psilostachya kz1" by Krzysztof Ziarnek Kenraiz - Own work. Licensed under Creative Commons Attribution-Share Alike 3.0-2.5-2.0-1.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Ambrosia_psilostachya_kz1.jpg#mediaviewer/File:Ambrosia_psilostachya_kz1.jpg

"Tissues Affected In Allergic Inflammation" by SariSabban - Sabban, Sari (2011) Development of an in vitro model system for studying the interaction of Equus caballus IgE with its high- affinity FcεRI receptor (PhD thesis), The University of Sheffield. Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Tissues_Affected_In_Allergic_Inflammation.jpg#mediaviewer/File:Tissues_Affected_In_Allergic_Inflammation.jpg

"Epipen". Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Epipen.jpg#mediaviewer/File:Epipen.jpg