Anaphylaxis:

It is a severe, life threatening systemic reaction that can affect all age groups. It can be fatal and in unfortunate circumstances easily causes death immediately, if quick action is not taken. Therefore, it should be treated as a medical emergency.anaphylaxis-map

It can be associated with multiple target organs, including skin (rash, itchy, swollen face, lips and eyes), airways/respiratory (voice changes,wheeze and breathing problem) and gastrointestinal (tingling mouth,difficulty in speaking or swallowing,stomach cramp, nausia,vomiting) and cardiovascular systems (drop blood pressure result in collapse, loss of conciousness). Death can occur within 5 minutes of an intravenous injection, insect stings may collapse a patient within 15 minutes and food reaction can cause respiratory arrest typically after 30-35 minutes.

According to the MHRA (Medicine and Health Care Products Regulatory Agency in the UK) while an individual notices the signs of a severe allergic reaction such as  swelling in the throat, change in voice, difficulty swallowing or breathing, wheezing,  dizziness, feeling faint and sudden tiredness adrenaline auto injectors (AAIs) should be used followed by seeking an emergency medical service. Mild symptoms  should be treated with anthistamines as anaphylaxis may preceded from mild to severe reaction.
 Any allergen can trigger the anaphylaxis however, the most commonly identified allergens are food, drugs and venoms (including wasp and bee stings).