Anaphylactic reactions (anaphylaxis)

Photo of a woman with breathing difficulties

An anaphylactic reaction is a strong allergic reaction that can normally be kept under control if treated immediately. It is important to know what to do in an emergency. For some people or in certain situations, it's also a good idea to have an emergency kit at hand.

Allergies arise if the body's immune system overreacts to substances (allergens) that are usually harmless. The symptoms often only affect the part of the body that comes into contact with the substance. For instance, when pollen or dust are breathed in, the symptoms occur in the airways. In anaphylactic reactions (anaphylaxis), the symptoms – some of which are severe – affect several parts of the body at once, and sometimes even the whole body. But in most cases anaphylactic reactions aren’t that extreme. It is important to get treatment soon enough, though.

It is estimated that about 1 out of 10,000 people have an anaphylactic reaction every year. This kind of reaction is often referred to as "anaphylactic shock." But anaphylactic shock is actually a particularly severe form of anaphylaxis, which can be fatal in rare cases: About 1 to 3 out of a million people around the world die of anaphylactic shock per year.

What are the signs of an anaphylactic reaction?

Depending on how severe they are, anaphylactic reactions usually affect the skin, the digestive tract, the airways and the cardiovascular (heart and blood vessel) system. The severity of the reaction can be described using four grades:

Table: What are the signs of an anaphylactic reaction?
Grade Skin
symptoms and non-specific symptoms
Digestive tract Airways Cardiovascular system
1 Itching, skin rash, hives, swelling of the skin      
2 Itching, skin rash, hives, swelling of the skin Nausea, abdominal cramps, vomiting Runny nose, hoarse voice, difficulty breathing High pulse, low blood pressure, irregular
3 Itching, skin rash, hives, swelling of the skin Vomiting, diarrhea, bloating, urge to have a
bowel movement ("poop")
Throat swelling, breathing difficulties, blue
skin and mucous membranes
Circulatory shock: not enough blood in organs,
circulation problems, loss of consciousness
4 Itching, skin rash, hives, swelling of the skin Vomiting, diarrhea, bloating, urge to have a
bowel movement ("poop")
Respiratory arrest (person stops breathing) Circulatory arrest (blood stops circulating)

Anaphylactic reactions can vary greatly from person to person, or from one reaction to the next. The symptoms may get worse within only a few minutes. They then often stay at the same level of severity for a while and then go away again on their own. The different symptoms may occur alone, after one another, or at the same time. They might return again within 24 hours, even if they have already been treated.

Early signs of anaphylaxis may include the following:

  • A metallic taste in your mouth
  • A burning sensation on the palms of the hands and soles of the feet
  • Burning, tingling or itching on the tongue or roof of the mouth
  • Feeling afraid
  • Headache
  • Confusion

What can trigger anaphylaxis?

The most common triggers of severe anaphylactic reactions in children are foods (usually peanuts, walnuts and hazelnuts, fish, chicken eggs or cow's milk), followed by insect venom and medication. In adults, the most common trigger is insect venom, followed by medication and foods.

Certain factors can increase the likelihood of anaphylaxis. These include physical exertion, alcohol and infections. Severe anaphylaxis is more common in older people, as well as in people with severe cardiovascular disease or poorly controlled asthma.

Anaphylactic reactions are also a possible side effect of allergen-specific immunotherapy (desensitization).

How should anaphylactic reactions be handled?

First and foremost, it is important to stay calm and

  • as soon as you notice mild symptoms of anaphylaxis, call the emergency services (112 in Germany and many other countries, 911 in the U.S.) and tell them that you think it's an anaphylactic reaction,
  • inform people around you so that they can help if necessary,
  • if you have an emergency kit with medication, use it as specified and
  • depending on the symptoms, lie down flat on your back or sit down (or help the person to do so).

If the symptoms are severe (e.g. breathing difficulties or loss of consciousness), the adrenaline (epinephrine) should be injected before calling the emergency services, if possible.

Keeping a sample of the potential trigger may make the easier.

Strenuous physical activities should be avoided. Whether it's best to lie down or sit down will depend on the symptoms. A lying position is more suitable in most cases. If the person is finding it hard to breathe, a (half-)sitting position is better. If they are unconscious, or drifting in and out of consciousness, the recovery position is safest. In the event of circulatory shock, elevating the legs improves blood circulation. It might be hard to put children into a particular position because they are often scared, and move around a lot. It is then better to pick them up and hold them.

What if no pulse can be felt?

If the blood stops circulating around the body, a pulse will no longer be felt. It is then important to start doing CPR (cardiopulmonary resuscitation) immediately. In other words:

  • Place your hands on the breastbone and – keeping your arms outstretched – press down repeatedly at a rate of 100 to 120 times per minute (about two times every second).
  • Trained first-aiders should also breathe into the person's mouth using a compression-to-breath ratio of 30 to 2. That means that after doing 30 heart compressions, they should breathe into the unconscious person's mouth or nose twice, then do another 30 compressions, followed by another two breaths, and so on.
  • The heart compressions shouldn't be stopped for longer than ten seconds.
Illustration: CPR – The first steps: a) Check consciousness, b) Check breathing, c) Dial 112 (or 911 in the U.S.)

CPR should be continued until the heart starts pumping again or the emergency services arrive.

How are anaphylactic reactions treated?

The main medication used in the treatment of anaphylactic reactions is adrenaline (also called epinephrine). It improves blood circulation, makes it easier to breathe and reduces swelling of the skin. Adrenaline starts working within a few minutes. It is usually injected into a thigh muscle. If it isn't effective enough, another injection can be given five to ten minutes after the first injection.

According to current recommendations, it is also a good idea to take an antihistamine and – depending on the situation – a steroid medication as soon as possible. Both of these medications take longer to start working than adrenaline, but aim to further reduce the allergic reaction.

If it’s thought that the person's heart might stop beating, adrenaline is injected into a vein, or put into a vein using an infusion (a "drip"). If their throat swells up and their airways tighten, they are also given adrenaline through a breathing mask, together with oxygen.

If their breathing and heartbeat become very weak, they are given oxygen through a breathing mask. Sometimes a tube has to be inserted into the person's windpipe to allow them to breathe, but that’s only rarely necessary. In the event of circulatory shock, the person is quickly given a lot of fluids through an infusion (drip) in order to stabilize their circulation.

What do emergency kits have in them?

Emergency kits can be used to quickly treat anaphylaxis. They can either be used by the person themselves or by other people who are with them. Emergency kits contain the following:

  • An adrenaline (epinephrine) injection with a device that helps you inject it, known as an auto-injector
  • An antihistamine in the form of a liquid or tablet
  • A steroid medication in the form of a suppository, liquid or tablet
  • In people who have : an inhaler to open up their airways
  • In people who tend to have breathing difficulties: an adrenaline inhaler to breathe in
  • Instructions explaining how to deal with anaphylaxis
  • A medical ID card that says who you are, what you’re allergic to and which doses of the medications should be used

Who can be given an emergency kit?

Doctors can prescribe emergency kits for people who

  • have had an anaphylactic reaction in the past, unless the trigger can be avoided (like most medications can).
  • are known to have mastocytosis. In this rare disorder, certain immune cells in the tissue start multiplying a lot. Mastocytosis can occur in various organs, causing symptoms such as stomach ache, itching, exhaustion and muscle pain.
  • have had an allergic reaction to peanuts, walnuts or sesame in the past. These foods are particularly likely to lead to anaphylaxis.
  • have an allergic reaction to even small amounts of an allergen (a trigger).

In Germany, the costs of emergency kits are generally covered by statutory health insurers if one or more of these criteria are met.

Patients can participate in patient education programs where they learn how to deal with anaphylaxis and how to use their emergency kit. It is also important to let other people (such as friends, family or colleagues) know how to use the emergency kit, in case they ever have to help.

Deutsche Gesellschaft für Allergologie und klinische Immunologie (DGAKI). Akuttherapie und Management der Anaphylaxie (S2k-Leitlinie). AWMF-Registernr.: 061-025. 2021.

Dhami S, Panesar SS, Roberts G et al. Management of anaphylaxis: a systematic review. Allergy 2014; 69(2): 168-175.

Perkins GD, Handley AJ, Koster RW et al. European Resuscitation Council Guidelines for Resuscitation 2015: Section 2. Adult basic life support and automated external defibrillation. Resuscitation 2015; 95: 81-99.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on August 21, 2023

Next planned update: 2026


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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