If you suspect anaphylaxis, use an epinephrine auto injector promptly and call for emergency help. The reaction can worsen quickly, and you should not wait for a rash, a definite diagnosis, or antihistamines to work before treating serious breathing or circulation problems.
Recognizing anaphylaxis symptoms—and when to use an epinephrine auto injector
Anaphylaxis is a potentially life-threatening allergic reaction that often starts suddenly and progresses rapidly. Warning signs include trouble breathing, wheezing, throat or tongue swelling, difficulty swallowing, faintness, collapse, or other signs of a problem with circulation. Skin symptoms such as hives, flushing, or swelling may occur, but they can be absent. Resuscitation Council UK notes that skin or mucosal changes are missing in up to 20% of cases.
A reaction after contact with a known allergen makes anaphylaxis more likely, but you may not know the trigger. If serious airway, breathing, or circulation symptoms develop, don’t wait for every symptom to appear or for certainty about the cause. If the person has a prescribed auto-injector, follow their emergency action plan and use it when anaphylaxis is suspected.
How to use an epinephrine auto injector
Auto-injectors differ, so follow the instructions for the specific device and any training you have received. The medicine should be injected into the mid-outer thigh. Use the device as directed by its manufacturer, including how to position it and how long to hold it in place. If you are helping someone, keep your fingers away from the needle end.
Do not delay the injection while trying to find a perfect technique. Intramuscular epinephrine (also called adrenaline) is the first-line treatment for anaphylaxis. Antihistamines may help some skin symptoms after the emergency is controlled, but they do not treat dangerous breathing or circulation problems and are not a substitute for epinephrine.
When to give a second dose
If serious breathing or circulation symptoms persist, or worsen, after the first injection, give a second dose if one is available and the person’s action plan or device instructions allow it. Resuscitation Council UK’s 2021 emergency guidance recommends repeating an intramuscular dose after five minutes if these problems continue. Timing can vary between local guidance and individual action plans, so learn the instructions for your region and device before an emergency.
Many US and UK recommendations advise having two doses available. Your clinician can tell you how many devices to carry and make sure you, family members, or other caregivers know how to use them. A second dose is not a reason to postpone calling emergency services.
What to do after using the injector
Call your local emergency number after using an auto-injector and explain that anaphylaxis is suspected and epinephrine has been given. Numbers include 911 in the United States, 999 or 112 in the United Kingdom, 112 in the European Union, and 000 in Australia. Follow the dispatcher’s instructions. Emergency assessment matters even if symptoms improve, because the reaction may need further treatment or monitoring.
While help is coming, have the person lie flat if possible and avoid letting them stand or walk suddenly. If lying flat makes breathing harder, allow a position that eases breathing without standing. Keep watching their breathing and responsiveness. If symptoms persist and a second injector is available, use it according to the action plan and local guidance.
There is debate about whether every person whose symptoms resolve promptly after one dose needs emergency transport. Researchers have noted that the safety of skipping emergency assessment in this situation has not been established. Don’t use that uncertainty as a reason to delay calling; follow your local action plan and emergency-service advice.
After the immediate emergency
Arrange follow-up with a clinician, ideally an allergy specialist, to assess the likely trigger, discuss ways to reduce future risk, and review your action plan and device technique. International guidance agrees that prompt intramuscular epinephrine is the first treatment, but many treatment questions are difficult to study in randomized trials. That limitation does not change the recommended first response to suspected anaphylaxis.
This guide cannot replace training or a personalized plan. If you or someone you care for is prescribed an auto-injector, ask a clinician or pharmacist to demonstrate the exact device and explain what to do if symptoms return.
