People who get severe allergic reactions or anaphylaxis Generally get them from insect stings, some medication, and food. More rarely, this severe reaction follows an allergy injection, after vigorous exercise or during anesthesia.

Whatever the cause, the body launches an emergency state of allergic reaction, flooding all systems with histamine and other chemicals. Capillaries and blood vessels expand (which explains the sensation of flushing and the dangerous drops in blood pressure, often described as feeling faint or going into shock), the bronchial tubes constrict (causing wheezing or difficulty in swallowing) and sometimes the throat and mouth swell, a dangerous symptom that can cause suffocation, coma and even death.

The early symptoms are usually quite noticeable, including a feeling of warmth or tingling in the skin and lips and an itchy rash, often between 10 seconds and 15 minutes after contact with the allergen. More extreme symptoms such as feeling lightheaded, dizzy, nauseated, having stomach cramps, hoarseness, difficulty in swallowing , breathing and a sense of panic follow rapidly. Lack of oxygen often turns the skin blue, too (a condition called cyanosis).

On Asthma: Not all people with asthma have allergies. Roughly 5 per cent of the population lives with asthma. A Generally accepted definition of asthma is that, it is a disease that is characterized by increased responsiveness of the trachea (windpipe) and bronchi (main airway) to some type of trigger that causes widespread narrowing of the airways that changes in severity either as a result of treatment, or spontaneously.