Anaphylaxis

Introduction
Anaphylaxis is a serious, life-threatening allergic reaction. The most common anaphylactic reactions are to foods, insects,latex, exercises, medications.

If someone allergic to a substance, their immune system overreacts to the allergen by releasing chemicals that cause allergy symptoms. 

The flood of chemicals released by immune system during anaphylaxis can causes to go into shock; blood pressure drops suddenly and airways narrow, blocking normal breathing.

Some are susceptible to a much more serious anaphylactic reaction. This reaction typically affects more than one part of the body at the same time.

Anaphylaxis requires immediate medical treatment, including an injection of epinephrine. 

Accurate diagnosis and successful management of allergies is essential.

Presentation 
Signs & symptoms

Symptoms of anaphylaxis generally begin within minutes to a few hours after exposure to a trigger.

The most common symptoms of anaphylaxis are hives (urticaria) and swelling of the skin (angioedema), which occur in 80 to 90 percent of reactions. Respiratory symptoms occur in about 70 percent of reactions, and are especially common in people who also have asthma or another chronic respiratory disease. Extremely low blood pressure causing lightheadedness, dizziness, blurred vision, or loss of consciousness (passing out) occurs in up to about 70 percent of reactions.(Uptodatecom, 2015)

●Skin – Itching, flushing, hives (urticaria), swelling (angioedema)

●Eyes – Itching, tearing, redness, swelling of the skin around the eyes

●Nose and mouth – Sneezing, runny nose, nasal congestion, swelling of the tongue, metallic taste

●Lungs and throat – Difficulty getting air in or out, repeated coughing, chest tightness, wheezing or other sounds of labored breathing, increased mucus production, throat swelling or itching, hoarseness, change in voice, sensation of choking

●Heart and circulation – Dizziness, weakness, fainting, rapid, slow, or irregular heart rate, low blood pressure

●Digestive system – Nausea, vomiting, abdominal cramps, diarrhea

●Nervous system – Anxiety, confusion, sense of impending doom

Triggers

●Foods – hen's eggs, cow's milk, peanuts, tree nuts, fish, wheat, soy, peanuts, tree nuts, fish, and crustaceans (shellfish such as shrimp) 

●Medications, such as antibiotics (penicillins and cephalosporins) and analgesics (aspirin, ibuprofen).

●Venom from insects, including bees, yellow jackets, wasps, hornets, and fire ants.

●Latex from natural rubber, found in some latex gloves, balloons, condoms, sports equipment, and medical supplies.

●Allergen immunotherapy ("allergy shots"), such as those given for the treatment of allergic rhinitis (hay fever).

●Exercise, either by itself, or after food ingestion (eg, wheat, celery, shrimp or other food) or after medication ingestion (eg, aspirin, ibuprofen).

●Less common triggers include exposure to airborne allergens (such as horse dander), human seminal fluid, cold water, or cold air.

(Mayoclinicorg, 2015)

Risk factors 

●Previous sudden severe allergic reaction involving the whole body

●Asthma and other chronic lung diseases

●Other diseases – People with cardiovascular disease, for example, and coronary artery disease, are also at greater risk of severe anaphylaxis.

Diagnosis

The diagnosis of anaphylaxis is based on symptoms that occur within minutes to a few hours after exposure to a potential trigger, such as a food, medication, or insect sting.

Tryptase is one of the natural chemicals released into the blood during an anaphylactic reaction. An increased amount of tryptase can sometimes be measured in a blood sample collected during the first three hours after anaphylaxis symptoms have begun.

Management 

Epinephrine is the only medicine that optimally treats anaphylactic reactions. It is most effective when it is given promptly, before symptoms become severe. Neither antihistamines, which mainly relieve hives and itching, nor asthma inhalers (puffers), which mainly relieve coughing and wheezing, can fully treat anaphylaxis effectively. These medications should not be substituted for epinephrine. (Uptodatecom, 2015)

References 

Mayoclinicorg. 2015. Mayoclinicorg. [Online]. [6 May 2015]. Available from: http://www.mayoclinic.org/diseases-conditions/anaphylaxis/basics/symptoms/con-20014324

Uptodatecom. 2015. Uptodatecom. [Online]. [6 May 2015]. Available from: http://www.uptodate.com/contents/anaphylaxis-symptoms-and-diagnosis-beyond-the-basics