What is an allergy? By Vicky

“The term allergy, often used interchangeably with hypersensitivity, refers to particular types of abnormal immune responses to antigens, which are called allergens in these cases.” (Fox, 2009, p. 515).

Symptoms of an allergy:

• Allergic rhinitis (chronic runny or stuffy nose)
• Conjunctivitis (red eyes)
• Allergic asthma (wheezing)
• Atopic dermatitis (urticaria, also known as nettle rash or hives; eczema – itchy skin)
• Severe cases can cause anaphylaxis

These symptoms result from the immune response to the allergen (discussed in more detail further on).

Allergens to be aware of:

• Grass and tree pollens (ragweed Ambrosia, responsible for hay fever)
• Dust mites (Dermatophagoides farina, living in and feeding on house dust, produce waste product particles often responsible for chronic allergic rhinitis and asthma)
• Food (e.g. cow's milk, eggs, wheat, soya, seafood, fruit and nuts)
• Fungal or mould spores (in the bathroom and other damp areas)
• Medication (e.g. penicillin, aspirin, anaesthetics)
• Nickel, rubber latex, preservatives and hair dyes (skin contact allergens)
• Pet skin flakes or dander (e.g. cat, dog, horse or hamster)
• Wasp and bee stings

Morris (2012) describes an allergy as being an adverse reaction to a protein in our environment. These proteins are called allergens, such as those found on pets, and in pollen or nuts and are usually harmless. Proteins are large molecules consisting of amino acids which our bodies and the cells in our bodies need to function properly. Enzymes, hormones and antibodies are proteins.  Amino acids are the building blocks of protein and there are twenty different amino acids which can be arranged in numerous different sequences making millions of different proteins. According to medicalnewstoday.com “Amino acids are organic molecules - they are made out of carbon, hydrogen, oxygen, nitrogen and sometimes sulphur.”

In people with an allergy, the body reacts to a specific allergen by releasing histamine from basophils and mast cells in the skin, lungs, nose or intestine. This causes inflammation and swelling.

O.k. so what are basophils, mast cells and histamine, I hear you ask???

Histamine is a hormone and plays a role in localised immune responses and in allergic reactions. So basically it is part of an immune response to foreign pathogens. It is produced and secreted by basophils and by mast cells found in nearby connective tissues, causing the symptoms related to allergies. Should you wish to find out more about the chemistry of histamine then check out these websites:http://www.news-medical.net/health/What-is-Histamine.aspx http://www.enotes.com/histamine-reference/histamine

 

Basophils are a type of white blood cell that are produced in the bone marrow http://coloncancer.about.com/od/glossary/g/basophils.htm  Basophils are found in the blood but also in many tissues of the body, protecting the body from bacteria and parasites. Basophils are involved in the inflammatory reactions in your body. When basophils are stimulated they release histamine and other enzymes. 

Mast cells are white blood cells and are found in the blood plasma. Mast cells are part of the immune system and they play an important role in allergic reactions because of their ability to produce and secrete histamine. During an immune response, a mast cell is stimulated by a specific type of antibody called immunoglobulin E or IgE. According to Blackburn (2012) “Antibodies are grouped into classes based on a chemical chain, or tail, attached to them. There are five classes of antibodies based on the specific amino acid sequence of the chains, A, D, E, G and M. All antibodies are called immunoglobulins, so they are referred to as IgA, IgD etc.” http://www.wisegeek.com/what-is-a-mast-cell.htm  

T helper cells are a type of white blood cell, that play an important role in the immune system. Morris (2012) describes that at birth “the immune system switches to be either allergy prone (TH2) or non-allergy prone (TH1), depending on genetics and environment. TH stands for T helper type white blood cells. TH1 immunity is good for fighting bacteria and viruses, and protecting against allergies. TH2 immunity is good at fighting parasite infections, but makes us more vulnerable to develop allergies.”

In people that are allergic, Fox (2009) describes it is the TH2 cells that are stimulated causing the immunoglobin E (IgE) antibodies attached to the tissue mast cells and basophils to bind to the allergen and secrete histamine instead of the usual IgG antibodies that circulate in the blood. Histamine then produces the symptoms of allergic reactions. 

In an article Morris (2012) discusses atopy, a families predisposition to allergies. My family, on my Mother’s side, all of us suffer from hay fever, quite severely. Morris (2012) suggests that global warming could impact on allergies such as hay fever with the “changing patterns of natural vegetation and more profuse pollen production.”

In the same article Morris (2012) suggests that “if there's a family history of allergies, a child is much more likely to switch on TH2 immunity. This promotes the manufacture of excessive amounts of allergy-related immunoglobulin E (IgE) in the bloodstream. This IgE latches on to harmless allergens and triggers allergic reactions.” 

Morris (2012) demonstrates how the symptoms of hay fever may occur, “If an inhaled pollen micro-particle gets attached to IgE in the nasal membranes, for example, this combined IgE/pollen complex causes mast cells to release naturally occurring defence chemicals called histamine. This leads to profuse nasal itching, tickling, sneezing and a watery mucus discharge.”

So why did a Mum have an allergic reaction from the smoke on her son’s clothes after he’d been to a party which had a bonfire???????

Good question, especially since when you research allergies smoke doesn’t tend to be one that’s added onto the average list!

Well it appears that some people can have an allergic reaction to certain types of wood. To view a wood allergy and toxicity list check out this website http://www.wood-database.com/wood-articles/wood-allergies-and-toxicity/#npc. Approximately 2% of the general population is allergic to wood dust and to the compounds found in wood according to the website AllergyTreatmentandSymptoms.com. Therefore people working in the wood industry have a predisposition to develop this allergy.

The article further describes it is the chemicals in wood called quinones that cause the specific wood allergen. According to Answers.com quinones are “Any of a class of aromatic compounds found widely in plants, especially the yellow crystalline form, C₆H₄O₂, used in making dyes, tanning hides, and photography.” If the body becomes exposed to the wood allergen either by the skin coming into contact with wood or breathing in the airborne wood particles then the immune system produces the antibody IgE as previously discussed which in turn releases histamine.

References:

Allergy Treatment & Symptoms.co (no date) Wood Allergy. Available at: http://allergytreatmentsandsymptoms.com/woodallergy.html (Accessed 12 April 2012).

Bass, P. (2010) About.com Asthma What is a Basophil. Available at: http://asthma.about.com/od/glossary/g/gloss_basophil.htm (Accessed 12 April 2012).

Blackburn, V. (2012) WiseGEEK. Available at: http://www.wisegeek.com/what-is-a-mast-cell.htm (Accessed 12 April 2012).

Dixon, S. (2009) About.com Colon Cancer. Available at: http://coloncancer.about.com/od/glossary/g/basophils.htm (Accessed 12 April 2012).

Fox, S. (2009) Human Physiology. 11^th edn. New York: McGraw-Hill.

Lewis, R. (1998) An Allergic Reaction – Overview The Mc-Graw-Hill Companies. Available at: https://www.google.co.uk/search?q=google+images&hl=en&client=firefox-a&hs=JCk&rls=org.mozilla:en-US:official&prmd=imvnsa&source=lnms&tbm=isch&ei=I7yKT4KyMcOKhQfLp7XqCQ&sa=X&oi=mode_link&ct=mode&cd=2&ved=0CBkQ_AUoAQ&biw=1366&bih=649#hl=en&client=firefox-a&hs=aGk&rls=org.mozilla:en-US%3Aofficial&tbm=isch&sa=1&q=histamine+and+mast+cells&oq=histamine+and+mast&aq=0S&aqi=g-S1&aql=&gs_l=img.3.0.0i24.355191l363540l8l364612l14l14l0l3l3l0l243l1245l7j3j1l11l0.frgbld.&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=9013d4206fc5f051&biw=1366&bih=649 (Accessed 12 April 2012).

Meier, E. (no date) The Wood Database by Woodworkers for Woodworkers. Available at: http://www.wood-database.com/wood-articles/wood-allergies-and-toxicity/#npc (Accessed 12 April 2012).

Morris, A. (2012)  BBC Health  Available at: http://www.bbc.co.uk/health/physical_health/conditions/in_depth/allergies/aboutallergies_what.shtml (Accessed 12 April 2012).

Nordqvist, C. (2010) Medical News Today. Available at: http://www.medicalnewstoday.com/articles/196279.php (Accessed 12 April 2012).