Anaphylaxsis

    Anaphylaxsis is type 1 hypersensitivity reaction which is life threatning.it can occur within seconds or minutes after exposing yourself to an allergen.Immune system gnerate antibodies inorder to defend against harmful.foreign substances sometimes th host response to allergen is excessive ,causing this response to be destructive while trying to be protective.over activity of immune system is at at the root of  hypersensitivity which underlies anaphylaxis.Anaphylaxsis can be catergorized into two types:

1. Systmic Anaphylaxsis
• occur after adminitration of variou drugs uh as pencilin,antisera,hormone and enzymes,or bite of honey bees.
• shock dose of antigen may be exceedlingy small,within minutes after exposure there may be skin reactions,constriction of airways and a swollen tongue,laryngeal sweeling,anaphylactic shock(hypotension) and even death
2. Local Anaphylaxsis-
• example of type 1 hyperensitivity is atopic allergy or atopi disorder.
• atopic is a genetic predisposition to form excessive Immunoglobin E(IgE).
• family history of allergy is found in about 50% of patients.
• several genes associated with atopy has been identified in atopic induviduals.the gene is IL-4 results in an increased amount of IgE synthesis by B cells.
• Many local  anaphylaxsis Occurs in two stages.
• immediate phase occurs within 5-30 minutes and may subside in an hour,histamine is the mediator.
• late phase ocurs in 2-8 hours later without additional exposure ot the allergen.it last for several days.

Examples

1. lung atopic asthama-it is produced when allregens inhaled such as pollens,house dust containing mites,fungul spores and animal feather/fur.ingeste allergens from shellfish,nut an yeast.
2. Nose and eyes-running nose and inflamattion of the outer memebrane of th eyeball and innerlid ue to hay fever pollens.
3. Intestinal tract:food allergy .peanuts,mik,eggs,soya and sheelfish.allergic gastroenteritis consists of nausea,vomitting and diarrhoea
4. Skin(atopic dermatitis)-with dust mites.,urticaria-due to variou foods and drugs

Diagnosis-

1. skin test-(sratch,patch ,injection)offending allergen is adminitered.apperane of ‘’flare and wheal’’ at the site of maximum within 30 minutes indicates positive test to the offending antigen.
2. 2Radioallergosorbent(RAST) -This is used to measure speiific IgE levels against potentilay offending allergens.
3. Immunologist will carryout an assesment inorder to findout the trigger  which induce hypersessitivity.you will be asked to keep a record of medication and food with resulting signs and symptoms.   

Management 

1. Avoidance of potential allergens
2. Acute desensitization-A veery small amount of antigen to which the invidual is hypersensitive is adminstered at 15 mins interval.antigen-IgE complexes form on a small scale major reaction.this permits adminitration of a drug or foreign protein to a hyperenitive person.hypersenstive returns.
3. Chronic desensititization-it involves injection of the allergens to which the induvidual is hypersensitive,IgG blocking antibody is produced which bins the offending allergen an prevents the antigen from reaching IgE on mast cells and thus prevent reaction.
4. Administer high flow oxygen at 10 liters per minute with a reservoir bag. 
5. Lay the patient flat to facilitate circulation. 
6. Administer IM adrenaline (epinephrine) in the anterolateral aspect of the mid-thigh.  Dose of epinephrine for adults and children above 12 years is 0.5mg while for children 6-12 years is 0.3mg and for children below 6 years is 0.15mg.  
7. If the client shows no clinical improvement with the initial adrenaline dose IM adrenaline should be repeated in 5 minutes. For clients who require multiple adrenaline doses, IV adrenaline can be administered. (IV adrenaline can be given as a bolus or an infusion and the administration should be done only by once who are having a special trainee and experience)

References

• Ferreira, Manuel Branco, and Rodrigo Rodrigues Alves. "Are general practitioners alert to anaphylaxis diagnosis and treatment?." European annals of allergy and clinical immunology 38.3 (2006): 83-86.
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• Mueller, D. L., & Noxon, J. O. (1990). Anaphylaxis: pathophysiology and treatment. Compendium on Continuing Education for the Practicing Veterinarian, 12(2), 157-170.
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• Uptodate.com, (2015). Anaphylaxis: Rapid recognition and treatment. [online] Available at: http://www.uptodate.com/contents/anaphylaxis-rapid-recognition-and-treatment [Accessed 29 Apr. 2015].