Using an adrenaline auto-injector for anaphylaxis, and why you still need to go to hospital afterwards

Which signs mean you should use an adrenaline auto-injector straight away?

Anaphylaxis gets worse quickly. It often starts within ten minutes or so of contact with the allergen, and in a few cases it can start up to about an hour later. It is not just a rash: several body systems are affected at the same time.

If any one of the following appears, especially in someone with a history of severe allergy, inject immediately using the method your doctor has taught you in advance. Do not wait:

Widespread urticaria (hives) and itching, together with tightness or swelling of the lips, eyelids or throat;

Difficulty breathing, wheezing, a hoarse voice, or difficulty swallowing;

Dizziness, a racing heart, pale skin, cold sweats, or feeling about to faint;

Ongoing abdominal pain or vomiting, together with any of the signs above.

Early on there may only be a vague feeling of unease, tingling or dizziness. This hard-to-describe discomfort is also worth paying attention to. In children it may show as sudden irritability, crying, or saying their tummy feels bad.

One thing to note: a mild local rash or simple nasal itching is usually not a reason to use the injector. For your own child or yourself, your doctor should explain the exact boundaries in advance.

Where to inject: the outer thigh, even through clothing

The standard site is the front outer thigh, the thickest part of the muscle, roughly midway between the hip and the knee. The muscle here is thick and has a good blood supply, so it absorbs faster than the buttock or the arm.

The key steps can be summed up in a few short points:

Hold the device straight against the skin, not at an angle;

You can inject through thin clothing; you do not need to find alcohol to clean the skin first;

Press down and keep pressing; after you hear or feel a "click", keep counting to the time specified;

The needle retracts automatically after you pull it out, but still handle the used device with care.

Choosing the outer thigh is a general rule. For children, people who weigh less, people taking anticoagulant medicines, and the specific device used, a doctor should demonstrate and confirm in person. The types of device available in China vary, so follow the instructions for use and your doctor's guidance rather than copying someone else's experience.

Why you must still go to hospital after injecting

Adrenaline is the first step, not the end point. It relieves symptoms quickly, but its effect does not last long, and anaphylaxis itself may keep developing.

After injecting, call for emergency help or go to the emergency department straight away, for three reasons:

Symptoms may get worse again, and a doctor needs to assess whether more treatment is needed;

Some people need oxygen, fluids, or further treatment of the airway;

After a severe reaction, delayed symptoms can appear, and the risk period needs to be spent under medical observation.

Even if you feel much better after injecting, do not stay at home to observe, and do not cancel going to hospital because "it's already better". On the way, lay the patient flat and raise their legs; if breathing is difficult, they can sit up. Do not let them stand or walk around.

How long to be observed, and what to watch for in a second reaction

Symptoms can come back several hours after the first improvement. They are usually milder than the first time, but can also be worse. For this reason, doctors usually ask you to be observed in the emergency department for several hours; the exact length is decided by the treating doctor based on how severe the reaction was.

During observation, watch for these changes:

Rash or swelling returning or getting worse;

Breathing becoming fast or noisy again, or difficulty speaking in full sentences;

Dizziness, a racing heart, or weakness returning;

A child becoming less responsive, sleepy, or unusually irritable.

After observation ends and you go home, someone should still stay with you for a short period. If breathing or circulation problems appear again, use the adrenaline auto-injector again and seek medical care immediately. Do not wait to see whether it settles on its own.

When to see a doctor: ask in advance

Besides an acute episode, there are several situations where you should see a doctor for assessment in advance:

You have had a severe reaction such as difficulty breathing, throat tightness, or fainting;

You have a known food or insect allergy, and each reaction is worse than the last;

You are not sure whether you are someone who needs an adrenaline auto-injector;

Your device is out of date, you do not know how to use it, or no one has ever shown you.

When you see the doctor, you can list your questions clearly: what are the indications for me or my child, which site to inject, what to do afterwards, how many devices to keep, and how to store and replace them. Emergency care arrangements differ between regions in China, so follow your doctor's and local emergency guidance for these details, and do not rely on online experience alone.

This article is for general information only and is not medical advice. Please follow your doctor's instructions.