Acute anaphylaxis: signs and emergency action

It may involve swelling of the tongue or throat, difficult or noisy breathing, wheezing, dizziness, collapse, or a sudden change in alertness. A rash or facial swelling can occur, but skin changes may be absent. Do not wait for every possible feature to appear before acting.

During anaphylaxis, immune chemicals can quickly narrow the airways, swell tissues and lower blood pressure. Symptoms can begin after foods, medicines, insect stings or another allergen, and the trigger is not always obvious at the time. Anaphylaxis can present with wheezing, throat tightness, a hoarse voice, persistent cough, widespread hives, vomiting or faintness.

A reaction affecting breathing or circulation is an emergency even if the person has no rash. Symptoms that settle can return, so medical observation is still needed after adrenaline has helped.

Use the person's prescribed adrenaline auto-injector without delay, following its device instructions, and call emergency services. If the trigger is still present and can be removed safely, such as an insect stinger, remove it without delaying adrenaline. Do not give food, drink or oral medicine to someone who is struggling to breathe or swallow.

Keep the person lying flat with legs raised when possible. Let them sit with legs extended if breathing is difficult, and place an unconscious person who is breathing in the recovery position. Avoid allowing them to stand or walk. If symptoms persist and another prescribed auto-injector is available, follow the person's emergency plan or the emergency call handler's directions.

Call emergency services immediately for swelling of the tongue or throat, trouble breathing, a hoarse voice, blue or grey lips, collapse, confusion, or severe dizziness after a possible allergen exposure. Give adrenaline first when it is available; antihistamines do not treat dangerous airway swelling or low blood pressure.

Hospital assessment is necessary after any suspected anaphylactic reaction, including when the person appears to recover. Clinicians can monitor breathing and circulation, treat returning symptoms, replace used auto-injectors and arrange follow-up for trigger investigation.

Ask what the likely trigger was, whether allergy testing is appropriate, how to avoid another exposure and which written emergency plan to follow. Check how to store, carry and use your specific auto-injector, when it needs replacement, and whether family, school or workplace contacts should be shown how to help.