*The UK incidence of anaphylactic reactions is increasing. *Patients who have an anaphylactic reaction have life-threatening airway and, or breathing and, or circulation problems usually associated with skin or mucosal changes. *Patients having an anaphylactic reaction should be treated using the Airway, Breathing, Circulation, Disability, Exposure (ABCDE) approach. *Anaphylactic reactions are not easy to study with randomised controlled trials. There are, however, systematic reviews of the available evidence and a wealth of clinical experience to help formulate guidelines. *The exact treatment will depend on the patient's location, the equipment and drugs available, and the skills of those treating the anaphylactic reaction. *Early treatment with intramuscular adrenaline is the treatment of choice for patients having an anaphylactic reaction. *Despite previous guidelines, there is still confusion about the indications, dose and route of adrenaline. *Intravenous adrenaline must only be used in certain specialist settings and only by those skilled and experienced in its use. *All those who are suspected of having had an anaphylactic reaction should be referred to a specialist in allergy. *Individuals who are at high risk of an anaphylactic reaction should carry an adrenaline auto-injector and receive training and support in its use. *There is a need for further research about the diagnosis, treatment and prevention of anaphylactic reactions.