How quickly can anaphylaxis happen?

Anaphylaxis is a severe allergic reaction affecting the airway, breathing, circulation, skin, or digestive system. It may follow food, medicine, an insect sting, or another trigger. Early signs can include widespread hives, swelling of the lips or tongue, throat tightness, coughing, [Wheezing](/symptoms/wheezing/), voice change, vomiting, dizziness, or collapse.

Symptoms often appear shortly after exposure, but timing is not identical for everyone. A person can become seriously unwell even if the first symptoms seem mild, and symptoms can return after they improve. The absence of a rash does not exclude anaphylaxis when breathing or circulation is affected.

Use an adrenaline auto-injector immediately if one has been prescribed and anaphylaxis is suspected, following its instructions. Call emergency services, say that anaphylaxis is suspected, and do not leave the person alone. Have them lie down with legs raised if this is comfortable; allow someone struggling to breathe to sit with legs extended. Do not let them stand or walk suddenly.

A second auto-injector may be needed if symptoms continue or return, according to the prescribed plan and emergency advice. Emergency clinicians can provide [Anaphylaxis Emergency Treatment](/treatments/acute-and-urgent-care/anaphylaxis-emergency-treatment/). Later, [Allergy Testing](/treatments/diagnostics-and-screening/allergy-testing/) may help identify a trigger.

Treat breathing difficulty, throat or tongue swelling, faintness, collapse, or rapidly spreading allergic symptoms as an emergency. Do not wait to see whether an antihistamine works, and do not drive yourself for emergency care. Anyone treated for suspected anaphylaxis needs medical assessment because symptoms can recur and the trigger may need investigation.

What symptoms should prompt me to use my auto-injector? Should I carry more than one? How should family, colleagues, or school staff help? What triggers should I avoid, and do I need an allergy action plan or referral?