Most allergic reactions are mild, causing itching, hives, or a runny nose, and can be managed with antihistamines and advice from a pharmacist. A reaction becomes a life-threatening emergency, called anaphylaxis, when it affects breathing or circulation.
Warning signs of anaphylaxis include swelling of the lips, tongue, mouth, or throat, a hoarse voice or tight throat, difficulty breathing or noisy wheezy breathing, sudden dizziness, feeling faint, a fast heartbeat, widespread hives with any of these features, or collapse. These can develop within minutes of exposure to a trigger such as a food, insect sting, or medication.
If anaphylaxis is suspected, use an adrenaline auto-injector straight away if one is prescribed, then call your local emergency number, even if symptoms start to improve, because reactions can return. Lie the person flat with legs raised unless they are struggling to breathe. Always seek emergency care after using an auto-injector.