Anaphylaxis is a severe form of allergy which can even kill the affected person. Usually within seconds to minutes of exposure to a potential allergen a susceptible person can develop anaphylactic reaction. Allergen can be peanuts, pollen or venom following bee sting. Exposure to an allergen may trigger the immune system of the susceptible person to release number of chemicals which are capable of precipitating anaphylactic reaction. Common presenting symptoms of anaphylactic reaction include rapid fall in blood pressure to a dangerously low level, sudden narrowing of airways sometimes complete blockage of the airways may also occur leading extreme breathing difficulty to complete stoppage of breathing, appearance of specific type of skin reaction, nausea, vomiting even passage of loose stool etc.

Anaphylaxis is a medical emergency requiring immediate medical attention. The affected person requires injection of adrenaline and other supportive measurements like intubation to keep the airway patent. If not treated timely and adequately anaphylaxis may lead to death.It is estimated that around the world about 2% of the total population experiences anaphylaxis at least once in their life time.
Symptoms
Usually the symptoms of anaphylaxis appear within minutes however in some it may take hours to develop the symptoms. Common presenting symptoms include :
1) Characteristic skin lesions; usually hives with intense itching and flushing or paleness of the adjacent skin is almost always present.
2) Warm sensation
3) Feeling of lump in the throat
4) Moderate to severe degree of difficulty in breathing as the airway becomes narrow and there is swelling of the tongue which may also obstruct the air passage
5) Feeble but rapid pulse rate
6) Nausea, vomiting, passage of loose stool
7) Sudden blackout may also occur
Symptoms of anaphylaxis can become life threatening thereby requiring immediate management. Death may occur due to blockage of the air ways or due to stoppage of the heart.

Causes
Immune system of the body targets the invading foreign substances like bacteria, viruses and other pathogens and releases various chemicals to destroy them, but it does not react in the same way towards the body’s own cells (self).Sometimes the immune system can wrongly become over activated against common otherwise harmless substances (allergen) triggering release of the chemicals. These chemicals in turn can precipitate symptoms of allergy. Usually allergy is not life threatening however in some people there is excessive release of the chemicals leading anaphylactic reactions.

Common causes of anaphylaxis include exposure to specific drugs like penicillin, foods like peanuts, tree nuts like walnut, almond, cashew, wheat (especially in children), fish especially sea foods, milk, eggs etc, insect bite like bite or sting by ants, bees, wasps, hornets etc.
Less commonly involved factors are latex, certain anesthetic drugs, immediately after exercise etc.The commonly involved drugs are aspirin, ibuprofen, naproxen, penicillin etc. Sometimes exposure to contrast agents (iodine containing dyes) used in imaging studies may lead to symptoms of anaphylaxis.

Exercise may trigger anaphylactic attack in some people. Sometimes even jogging and other common aerobic exercise may trigger anaphylaxis while in some people even walking may precipitate an attack. Taking specific food in specific weather condition like in extreme heat or in extreme cold may precipitate an attack of anaphylaxis.In some people the exact triggering factor for anaphylactic reaction may not be identified; these cases are considered to be idiopathic.
 
Risk factors
Many people do not know the triggering factor anaphylactic attack in them still some of the well known and established risk factors for anaphylaxis are
1) personal history of suffering from anaphylaxis in the past
2) suffering from other forms of allergy, asthma
3) people with family history of anaphylaxis are at increased risk of suffering from anaphylactic attack themselves in comparison to persons who do not have any positive family history for anaphylaxis.

Treatment
Anaphylactic attack is treated on emergency basis. If the heart functions and breathing are stopped then cardiopulmonary resuscitation (CPR) is started. Along with CPR certain other drugs are also given like adrenaline (the drug of choice in anaphylaxis), oxygen inhalation, intravenous corticosteroids and antihistamine drugs to facilitate breathing and reduce inflammatory changes also beta 2 agonists are like salbutamol are also given to relieve shortness of breathing.

People with history of anaphylactic reaction are advised to carry an autoinjector which consist of a syringe and a hidden needle with single dose of adrenaline, all the time. So that during emergency he or she can self administer the life saving dose of adrenaline before reaching the hospital.
Other than allergy shots (which is not very much successful in preventing anaphylactic attack in every susceptible person) there is no other way to prevent the immune system from releasing inflammatory mediators following exposure to allergens.However following steps can be taken to prevent future attacks; these are avoiding the known triggering factors, always carrying the autoinjector containing adequate amount of adrenaline, taking steroids or antihistaminic drugs as per doctor’s advice.