Anaphylactic shock or anaphylaxis



Anaphylactic shock or anaphylaxis is a severe and life-threatening allergic reaction. It starts suddenly and gets worse very quickly: it can occur after a few seconds or minutes of exposure to something you are allergic to, such as peanuts or the venom injected by bee stings.

Anaphylactic shock is an "emergency that requires very rapid medical intervention.

In the event of anaphylactic shock, the body's natural defense system (immune system) releases a series of chemicals that cause a sudden drop in blood pressure and a restriction of the airways with blockage of breathing.

Signs and disorders (symptoms) that may appear in anaphylactic shock include:

  • fast and weak heartbeat
  • urticaria
  • nausea and vomit

More common triggers (different from person to person) include allergic shocks to:

  • foods
  • medications
  • insect poison
  • latex

Anaphylactic shock requires an injection of adrenaline and first aid. In any case, an ambulance must be called immediately and taken to the emergency room. If anaphylactic shock is not treated immediately, it can be fatal.

In case of symptoms (symptoms) associated with anaphylactic shock, one should:

  • call 118 immediately, asking for an "ambulance to be sent
  • stretch the person with the belly up (supine), unless you are unconscious, pregnant or having difficulty breathing
  • carefully remove any triggering cause, for example the sting of a bee
  • use an adrenaline auto-injector, if available and you are able to use it correctly
  • give another injection of epinephrine after 5-15 minutes, if the symptoms (symptoms) do not improve and a second drug auto-injector is available


Disorders (symptoms) caused by anaphylactic shock include:

  • lightheadedness, dizziness, collapse or loss of consciousness
  • lowering of blood pressure (hypotension), and a fast, weak heartbeat
  • respiratory difficulties (dyspnoea), with fast and shallow breathing
  • constriction of the airways and swelling (edema) of the tongue or throat, which can cause wheezing and trouble breathing
  • sweating
  • nausea, vomiting or diarrhea
  • confusion and anxiety
  • urticaria (rash), itching and redness of the skin or paleness

If a person is aware of a severe allergy or has already had anaphylactic shock, it is important to try to prevent future episodes:

  • identifying any triggers
  • avoiding triggers, When possible
  • always carrying an adrenaline auto-injector with you


The symptoms (symptoms) of an "allergy are usually not life threatening, but a severe allergic reaction can cause anaphylactic shock that becomes even more severe after" subsequent exposure to the first.

An anaphylactic reaction can be life-threatening because it can stop breathing or heart beating.

Anaphylactic shock is caused by an overreaction of the immune system (the body's natural defense system) against a trigger.

The most common causes of anaphylactic shock include:

  • foods, including nuts, milk, fish, shellfish, eggs, and some fruits
  • medicines, including some antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs)
  • insect bites, especially wasps and bees
  • substances used for general anesthesia
  • contrast media, used in diagnostic imaging investigations (e.g. CT scan)
  • latex, a type of rubber found in some types of rubber gloves and condoms

The increased risk of developing anaphylactic shock includes:

  • previous anaphylactic shock, subsequent reactions may be more severe than the first
  • allergies or asthma, people with both conditions are more at risk of having anaphylactic shock
  • other conditions, including heart disease and the abnormal accumulation of a type of white blood cell (mast cell)

In some cases, the cause of anaphylactic shock cannot be identified (idiopathic anaphylaxis).


Doctors ask about any previous allergic reactions, including those to:

  • foods
  • medications
  • latex
  • insect bites

To ascertain (diagnose) that it is precisely anaphylactic shock, the doctor will have to:

  • exclude other conditions , with signs and disorders similar to those of anaphylaxis
  • do skin tests or blood tests, to determine the triggering cause of anaphylaxis (Prick test, Patch test)
  • measure the amount of the tryptase enzyme released by mast cells into the blood, which can be elevated up to three hours after the onset of anaphylaxis


Anaphylaxis is an emergency that requires immediate medical attention and treatment.

Cardiopulmonary resuscitation (CPR) may be required if breathing is blocked or cardiac arrest occurs during anaphylactic shock. The use of drugs is also possible, including:

  • adrenaline (epinephrine), to reduce the allergic response
  • oxygen, to help with breathing
  • intravenous antihistamines and cortisone, to reduce airway inflammation and improve breathing
  • beta-agonists (such as albuterol), to relieve respiratory ailments (symptoms)

What to do in an emergency

For signs of anaphylactic shock (paleness and cold sweat, weak and rapid pulse, difficulty in breathing, confusion and loss of consciousness):

  • emergency call to 118
  • administration of adrenaline (epinephrine), through an auto-injector, if available
  • positioning of the person lying with the legs raised
  • pulse and breathing control, if necessary, perform heart massage or other first aid measures

Use an auto injector

People with potentially severe allergies are often prescribed adrenaline auto-injectors to carry with them at all times. This device consists of a syringe (combined with a hidden needle) that injects a single dose of the drug when pressed against the thigh. Always check the expiration date, otherwise the drug may not work properly.

Immediate use of an auto-injector can prevent shock from worsening and could be life-saving.

People with allergies should learn how to use the auto-injector and make sure that the closest people know how to use it.

Positioning and resuscitation

In case of anaphylaxis, the person should be placed in a comfortable position and should remain lying down except in the case of:

  • pregnancy, pregnant women should lie on their left side to avoid putting too much pressure on the large vein that carries blood to the heart
  • difficulty in breathing, the person should remain seated to facilitate breathing
  • unconscious situation, the person should be placed in the recovery position to ensure that the airways remain open and free: place them on their side, making sure they are supported by one leg and arm, and open the airway by lifting the chin
  • respiratory or cardiac arrest, in this case, cardiopulmonary resuscitation should be performed immediately

In addition, a sudden change in posture (standing or sitting) must be avoided, which can cause a dangerous drop in blood pressure.


The best way to prevent anaphylaxis is to avoid the substances that cause this severe reaction.

  • wear a medical alert bracelet, in which allergies to specific drugs or other substances are indicated
  • have an emergency kit available with medications prescribed by your doctor, check the expiration date of the adrenaline auto-injector, replace it before it expires and store it at room temperature (15-25 ° C).
  • warn doctors about allergic reactions to drugs

In case of allergy to avoid insect bites:

  • wear pants and long-sleeved shirts
  • do not walk barefoot in the grass
  • avoid bright colors
  • do not wear perfumes, colognes or scented creams

For known food allergies:

  • carefully read the labels of the foods purchased

In case of meals eaten away from home:

  • ask for the ingredients of each disheven small amounts of the food you are allergic to can cause a severe reaction


NHS. Anaphylaxis (English)

Mayo Clinic. Anaphylaxis (English)

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