If the condition is caused by a food allergy, the main symptom is usually severe swelling of the lips, tongue and throat, which makes it very difficult to breathe. In cases involving insect stings or injected drugs, the main symptoms are to do with the heart and circulatory system. These symptoms include low blood pressure and a weak pulse. The person may feel dizzy and faint and may feel a sense of doom. Other symptoms include abdominal pain, nausea and vomiting, urticaria, asthma and perennial allergic rhinitis.
Symptoms usually develop within minutes of coming into contact with the allergen.
Anaphylaxis progresses so quickly, that treatment must be given as soon as possible - preferably within minutes. Emergency treatment consists of an injection of a drug called adrenaline, which raises blood pressure, relieves breathing difficulties and reduces swelling. Once adrenaline has been given, people normally recover quickly. However, people who have had anaphylaxis should always go to hospital for observation. This is because they may need further treatment, such as oxygen, rehydration, antihistamines or anti-inflammatory drugs called corticosteroids.