Allergic Reaction
An allergic reaction is an immune response to a trigger such as food, medicine, venom or latex, producing symptoms that range from a local rash to life-threatening anaphylaxis.
Key points
- Breathing difficulty, throat or tongue swelling, faintness or symptoms in several body systems indicate possible anaphylaxis.
- Antihistamines can ease itch or hives but do not replace adrenaline in anaphylaxis.
- Identifying the trigger and documenting the timing of exposure helps prevent recurrence and guides allergy assessment.
The listings below are not appropriate for treating a severe reaction without emergency care or for confirming its trigger.
Recognising severity
Mild reactions may remain limited to itchy skin, hives or local swelling. Anaphylaxis can progress quickly and may involve the airway, breathing or circulation, sometimes with vomiting or widespread hives. Skin symptoms can be absent, so do not wait for a rash when breathing or faintness develops.
After the immediate episode
People at risk may need adrenaline auto-injectors and a written action plan. A clinician can review suspected triggers, cofactors and whether formal allergy testing is useful. Medicine allergies should be recorded precisely rather than applying a broad label without evidence.
When to seek urgent care
Call emergency services for swelling of the tongue or throat, breathing difficulty, wheezing, faintness, collapse or a rapidly progressing reaction involving more than one body system. Use prescribed adrenaline immediately when the action plan says to.