Anaphylactic Shock and Acute Allergic Reaction

Useful links – The Anaphylaxis Campaign

Anaphylactic shock is an extreme allergic reaction. What is an allergic reaction? Life threatenig allergic reaction

Picture thanks to the Anaphylaxis Campaign

Allergic reactions occur because the body’s immune system reacts inappropriately in response to the presence of a substance that it wrongly perceives as a threat. In order to develop an allergic response the body has to be exposed to something in order to trigger the immune response. This can be touched, inhaled, swallowed or injected – during a routine vaccination or by an insect sting. anaphlylactic reaction-01 The body doesn’t react to the irritant directly. It reacts to the histamine released by cells damaged through the immune response on subsequent exposure. Everyone makes IgE, but people with allergies produce more of it. When someone with an allergic predisposition is initially exposed to an allergen, they produce a lot of IgE antibodies. These bind to the mast cells in the tissues or basophils in the blood. When the IgE line up next to each other, the reaction affects the membrane and causes the cell to break down (degranulation). The breaking down of these cells releases histamine and other chemicals. Histamine dilates blood vessels and makes them more permeable. Therefore, they lose fluid causing swelling in the tissues.

This mechanism is so sensitive that minute quantities of the allergen can cause a reaction. The released chemicals act on blood vessels to cause the swelling in the mouth and anywhere on the skin. There is a fall in blood pressure. In asthmatics the effect may be mainly on the lungs, causing a severe asthma attack which their inhaler is unable to help. We have small amounts of histamine in our system normally. It is important for various vital functions of the body including regulating stomach acid and as a neurotransmitter in our nerve cells. However larger amounts of histamine being released leads to symptoms such as sneezing, blocked nose, itching… the sort of symptoms often associated with hayfever and mild allergies.

Antihistamine medication

Antihistamine medication can work effectively at resolving these symptoms. However Antihistamine medication typically takes around 15 minutes to work. Life threatening and systemic allergic reactions are caused by the body producing even more histamine. This dilates small blood vessels and causes them to leak, resulting in swelling in areas such as the lungs – leading to breathing problems. Sufferers may have a rash and be flushed due to the increased blood supply to the skin.

Their blood pressure could drop dramatically and they may collapse. The more times someone is exposed to the substance they react to, the quicker and more severe the reactions may be. If they don’t have a rash associated with the symptoms, it could still be an anaphylactic reaction. If they have a rapid onset of symptoms and may have been exposed to an allergen, treat as an anaphylactic reaction.

Who is at risk from anaphylaxis?

It is thought that people inherit the predisposition to react to a particular allergen, combined with environmental factors. People can develop reactions to things that have never previously been a problem. If there is a family history there is a far greater chance of someone having allergic tendencies. If a patient has suffered a bad allergic reaction in the past – whatever the cause, this may make them more prone to having further severe reactions. If a significant reaction to a tiny dose occurs, or a reaction has occurred with just skin contact, this could indicate that they are sensitive to this particular allergen and greater contact could lead to a more severe attack.

Asthma can put a patient in a higher risk category. Most schools have at least one child at risk of acute allergic reaction. It is of crucial importance that anyone caring for a child with a history of anaphylaxis has detailed medical information about the children and precisely what the children are allergic to and what other products or foodstuffs may contain these allergens. Even some obscure products that you would not associate with allergens can contain them. Thus, if a child appears to be having a reaction, with no obvious trigger, use their adrenaline auto injector if indicated and get emergency help quickly.

Teachers should think of all aspects of the school environment and ensure that children are not exposed to triggers when doing craft, junk modelling, cookery and all other aspects of the curriculum.

Common triggers for allergic reactions

Individuals can react to absolutely anything. However most common causes include foods: such as peanuts, tree nuts (e.g. almonds, walnuts, cashews, and Brazil nuts), sesame, fish, shellfish, dairy products and eggs. Non-food causes include wasp or bee stings, natural latex (rubber), penicillin or any other drug or injection. Exercise can also trigger a delayed allergic reaction following exposure to an allergen.

Triggers for anaphylaxis

Common triggers of allergic reaction and anaphylaxis

How to recognise an acute allergic reaction?

Child having an allergic reaction      Hives from an acute allergic reaction

A reaction can take many forms and people who have reacted one way when exposed to a particular allergen can react completely differently on another occasion when exposed to the same thing. It is therefore extremely difficult to predict what a reaction might look like. The above picture is a very classic reaction and easily recognisable as Anaphylactic shock. Common symptoms include: Generalised flushing of the skin A rash or hives anywhere on the body A feeling of anxiety or ‘sense of impending doom’ Swelling of throat and mouth and difficulty in swallowing or speaking Alterations in heart rate – usually a speeding up of the heart Severe asthma attack which isn’t relieved by their inhaler Acute abdominal pain, violent nausea and vomiting A sudden feeling of weakness followed by collapse and unconsciousness A patient is unlikely to experience all of the above symptoms.

How to Treat Anaphylaxis

The key advice is to avoid any known allergens if at all possible. If someone is having a mild allergic reaction, an antihistamine tablet or syrup can be very effective. However the medication will take at least 15 minutes to work. If you are concerned that the reaction could be systemic (all over) and life threatening, use an adrenaline auto-injector immediately. It is far better to give adrenaline and not to have needed it, than to give it too late.

Adrenaline auto-injectors are prescribed for those believed to be at risk. Adrenaline (also known as epinephrine) acts quickly to constrict blood vessels, relax smooth muscles in the lungs to improve breathing, stimulate the heartbeat and help to stop swelling around the face and lips. Acute Allergic reactions can be life threatening and it is crucially important that you recognise the problem and know what to do quickly in order to save someone’s life.


Adrenaline (US name: Epinephrine) is the first choice for an acute anaphylactic reaction. It works best if you give it as soon as you recognise that someone is having a reaction. You should administer the injector, or help the sufferer to administer it themselves, as quickly as possible. Call for an ambulance stating clearly that the person is having an acute anaphylactic reaction. Adrenaline should rapidly treat all of the most dangerous symptoms of anaphylaxis, including throat swelling, difficulty breathing, and low blood pressure.

However they are likely to need additional medication in hospital to control the reaction. Human body metabolises adrenaline very quickly.

It is very important that you call an ambulance as soon as you have given an auto-injector as its effects can wear off within about 15 minutes. You can give another injector 5-15 minutes after the first if necessary.

How to use an Adrenaline Auto-injector

Types of Auto-injectors:

There are currently 3 makes of Adrenaline Auto-injectors on the market in the UK; EpipenJext and Emerade. They all contain adrenaline and you can give them all in a similar manner. Epipen is by far the most popular in the UK. If you receive the prescription for an adrenaline auto injector you should carry it with you at all times and register to receive a reminder when it is going out of date. If you have been prescribed 2 adrenaline injectors as a duo pack, you should carry both with you at all times in case a second dose is needed.

Teach friends and family what to do if they need to help you or someone else having an anaphylactic reaction. Videos showing how to use adrenaline auto-injector are available on the drug company websites.

If you have to use an auto injector hold it in your dominant hand, with the other hand remove the safety cap. Put the injector firmly into the upper outer part of the casualty’s thigh and hold it there for 10 seconds. Remove it carefully and they should begin to feel better quite quickly. If they continue to get worse, you may need to give another injector. The auto-injector can be given through clothes. Always phone an ambulance.

Patient Positioning for anaphylaxis

Someone suffering from acute anaphylaxis is also likely to be showing signs of clinical shock. Reassuring the casualty and positioning them appropriately can make a major difference to their treatment. You should also be kept warm and dry. If someone is very short of breath, you should encourage them to sit, in an upright position to help their breathing. Putting something under their knees to help increase their circulation can be very helpful – into the lazy W position. If they are not having difficulty breathing, but are feeling sick, dizzy and could be going into shock. They should lie down with their legs raised to help increase the circulation to their vital organs. Encourage them to turn their head to one side if they are likely to vomit. Cover them to keep them warm and keep them in this position until the paramedics arrive. Do not get them up until paramedics has assessed their conditions.

Treatment for shock, lie down with legs raised

Treatment for shock

Treat for shock if they are showing symptoms of shock and are not having breathing problems – lie them down with their legs raised. If they are having breathing problems – sit them in the lazy W position. After an anaphylactic reaction: An ambulance should always be called if someone is showing the signs of anaphylaxis and they will usually be admitted overnight for observation. This is because some people have a second reaction some hours after the first. Don’t forget to replace the used adrenaline auto-injector.

We strongly recommend that you complete an online or attend a practical or online first aid course to understand what to do in a medical emergency. Click here or call 0208 675 4036 for more information about our courses. First Aid for Life provides this information for guidance and it is not in any way a substitute for medical advice. First Aid for Life is not responsible or liable for any diagnosis made or actions you may take on the basis of this information.

Coronavirus disease (COVID-19) Information - As Essential First Aid Training We Continue to Run Face-to-Face First Aid, Blended and Online Courses. Click here to learn more...

FREE online choking course

NO credit card required!


Thanks! Please check your email to find out how to log in and get started. It may take up to 2-3minutes to arrive.

Share This