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Anaphylaxis is the term for a very severe type of allergic reaction. Also known as an anaphylactic reaction or shock, it typically develops suddenly without any warning, and can also progress and get worse very quickly.

According to Patient, the number of people who are affected by anaphylaxis is increasing, with around one to three reactions per 10,000 people in the UK each year (i). However, this may be an underestimation, as anaphylaxis isn’t always reported or recognised. It’s also thought that anaphylaxis is more common in females.

What are the symptoms?

As well as starting suddenly, the symptoms of anaphylaxis can be severe and frightening. These include breathing difficulties or noisy breathing, wheezing, a persistent cough, a hoarse voice, rapid heartbeat and swelling of the face, lips, eyes, tongue or throat. You may feel lightheaded or faint and become weak and floppy with an overwhelming sense of fear, as if something terrible is going to happen. And if your blood pressure falls dramatically, it can lead to collapse and unconsciousness. Other symptoms can also include clammy skin, a rash (hives), stomach pain, nausea and vomiting.

These symptoms are the result of your immune system overreacting to a trigger. This, says the NHS, is often something you’re allergic to, such as a type of food (ii). But the trigger isn’t always an allergen, and sometimes there’s no obvious trigger at all (this is called idiopathic anaphylaxis).

Common food triggers include the following:

  • Peanuts

  • Tree nuts (Brazil nuts, walnuts, cashew nuts, hazelnuts, almonds etc)

  • Fish and shellfish

  • Eggs

  • Cow’s milk

  • Sesame seeds

  • Soya

  • Kiwi fruit

Non-food triggers that can cause anaphylaxis include insect venom (bee or wasp stings, for instance), latex and medicines such as antibiotics, painkillers classed as non-steroidal anti-inflammatory drugs (NSAIDs), general anaesthetics and local anaesthetics. Very rarely, someone can experience anaphylaxis as a result of doing physical activity (exercise-induced anaphylaxis).

What happens?

Anaphylaxis works in the same ways as any other allergic reaction, but with more severe results. When your immune system reacts inappropriately to a food or substance that it wrongly believes is a threat, it can go into overdrive.

In anaphylaxis, specific types of antibodies on mast cells and basophils react with an allergen, causing what’s classed as a type 1 hypersensitivity reaction. This triggers the rapid release of a substance called histamine and makes the capillaries – the body’s smallest blood vessels – become leaky. Losing all this fluid from the bloodstream makes your blood pressure plummet, which in turn means your major organs don’t get the blood they need – this is what medical professionals call shock, or more specifically in this instance, anaphylactic shock.

When this happens, it should be treated as a medical emergency (call 999 for an ambulance). For more advice on what you should do in the event of an anaphylactic reaction, read the government’s online advice.

If you’re worried you may have a severe allergy see your GP as soon as possible. If necessary you’ll be referred to an NHS allergy clinic. And if you’re diagnosed as having a serious allergy, you must get to know what your triggers are so you can avoid them as much as possible, as well as carry a device called an adrenaline auto-injector with you at all times, which you must use whenever you think you may be experiencing anaphylaxis.

Meanwhile, if you’re not sure your allergy is severe enough to cause anaphylaxis, don’t let that put you off seeing your GP. Even if it turns out your allergy isn’t severe, it’s better to be safe than sorry.

Anaphylaxis in children

Experts claim it’s mostly children and young adults who are affected by anaphylaxis. According to the Anaphylaxis Campaign, every school is likely to have at least one pupil who is severely food allergic, and many schools will have more (iii). Food is a common trigger in children, with one in 70 thought to be affected by a peanut allergy (iii).

Other common allergens in children are fish, milk and egg, with allergies to tree nuts and other foods such as sesame seeds and shellfish happening less often.

If your child has allergies, it’s important that the staff at their school are fully aware of it, including what your child should avoid, food or otherwise.

Some members of a school’s staff should also be properly trained in preventing an allergic reaction and recognising the symptoms of allergic reactions and anaphylaxis, as well as what they should do in a medical emergency (this includes knowing how and when to use an adrenaline auto-injector).

It’s advisable to make sure the school has an emergency kit for your child – which should include medication such as antihistamines and adrenaline auto-injectors. This should be easily accessed by school staff, who should know where the kit is stored. It’s also important that the kit is kept up to date.

Meanwhile, make your child aware of any foods they shouldn’t eat, and explain the dangers of sharing food with friends during their lunch break. If they have school dinners, it’s essential that the school and the meal providers are aware of any foods they’re allergic to.

Making a management plan

The Anaphylaxis Campaign advises parents to organise an allergy management plan for every child who has allergies (iii). This can be compiled with help from your GP or allergy specialist, and a copy kept at your child’s school. The type of information it should contain includes the following:

  • Your child’s name, address and date of birth.

  • Your contact details – home, office and mobile telephone numbers – plus those of another person who can be contacted if you’re out of reach.

  • Contact details for your child’s GP.

  • A list of your child’s allergies (including things they should avoid).

  • A list of possible symptoms.

  • Details of your child’s medication.

  • Details of what to do in an emergency (including how to administer their medication).

  • A list of teachers and other staff members who have been trained to help.

  • Your written consent for staff to be responsible for administering medication.

Visit the British Society for Allergy and Clinical Immunology's website for a downloadable children’s allergy action plan.

Anaphylaxis and food

Currently there are 14 food allergens that must be labelled or indicated as being present in ingredient lists whenever they appear in pre-packed foods (iv). These include the following:

  • Cereals containing gluten: wheat (including varieties such as spelt and khorasan wheat), rye, barley, oats. If you react badly to gluten, you could be suffering from coeliac disease.

  • Crustaceans for example prawns, crabs, lobster, crayfish.

  • Eggs.

  • Fish.

  • Soybeans.

  • Milk (including lactose).

  • Tree nuts: almonds, hazelnuts, walnuts, cashews, pecans, Brazil nuts, pistachio and macadamia nuts.

  • Celery (including celeriac).

  • Mustard.

  • Sesame seeds.

  • Sulphur dioxide/sulphites, where added and at a level above 10mg/kg or 10mg/L in the finished product (this is often used as a preservative in dried fruit).

  • Lupin – including lupin seeds and flour – which can be found in types of bread, pastries and pasta.

  • Molluscs including mussels, whelks, oysters, snails and squid.

Here are some of the facts on the most common of these food allergens:

Cow’s milk

There are three main types of milk allergy: immediate onset cow’s milk allergy, where symptoms happen straight away; delayed cow’s milk allergy; and lactose intolerance. Cow’s milk allergy most often affects babies and young children, with most developing symptoms before they reach the age of six months. Affected children should initially avoid milk in all forms, including cream, cheese, yoghurt, butter (and other butter products), ice cream, fromage frais and crème fraiche.

Many other foods contain milk protein, including crisps, snacks and ready meals. Always check your food labels to make sure (also check for ingredients such as casein, whey, sodium caseinate and calcium caseinate, all of which are types of milk protein).


A common cause of allergic reaction in babies and young children, eggs can also cause reactions in teenagers and, less frequently, adults (many children outgrow egg allergy). Some may have immediate symptoms after coming into contact with egg, while others may have delayed symptoms. According to the Anaphylaxis Campaign, some very sensitive people may even suffer breathing problems when they inhale the fumes of cooked eggs (v). In the UK, many children who have an allergy to eggs also develop eczema. Why not read our article on eczema to find out about treatment and support.


Peanut and tree nut allergies can sometimes cause severe allergic reactions. If you or your child has a nut allergy, it’s essential to watch out for foods that contain nuts by reading all your food labels carefully (many products that you wouldn’t think contain nuts often do, including confectionary, ice cream, salad dressings and curries). If a food label states its contents ‘may contain’ nuts, it means there’s a risk the food or one or more of its ingredients have come into contact with nuts during the manufacturing process.

When eating out, be very vigilant, and make sure the restaurant staff realise you or your child has a nut allergy. Other things to look out for if you have a nut allergy are sesame seeds, and a legume called lupin, as you may react to these too.

Wheat and gluten

Wheat allergy is most common in children, but according to the Anaphylaxis Campaign, they usually outgrow it in the pre-school years (vi). Indeed, wheat allergy in adults is thought to be rare. When it does occur in adults, it is usually associated with exercise (that is, if they eat wheat but don’t exercise, they don’t get any symptoms).

Wheat allergy isn’t the same as a reaction to gluten, which is a protein found in wheat, rye, barley and oats. If you react to gluten, you have coeliac disease, a chronic autoimmune condition that causes gastrointestinal symptoms

Fish and shellfish

Fish – such as cod, plaice, haddock, herring, trout, salmon and tuna, to name just a few varieties – are all capable of triggering allergic reactions. However, there’s no evidence to suggest those who are allergic to fish have an increased risk of having an allergy to shellfish, and vice versa.

Shellfish are divided into two groups – crustaceans (crab, lobster, prawns, crayfish) and molluscs (mussels, oysters, scallops, periwinkles, squid etc). If you have an allergy to one type of crustacean or mollusc, there’s a good chance you’ll be allergic to one or more other types too (some people may react to both crustaceans and molluscs, thought this may be a result of cross-contamination on fish counters or in fish markets).

Anaphylaxis: non-food allergens

Food isn’t the only thing that can cause severe reactions in certain people. For instance, it’s estimated that about half a million people in the UK have had an anaphylactic reaction to bee or wasp stings (vii).

Insect venom

Being stung by a bee or wasp isn’t fun for anyone, but for most people it’s not dangerous. If, however, you react severely to the venom, you may experience anaphylaxis if you’re stung by the same insect again.

If you’ve had a systemic allergic reaction after being stung – that is, if you’ve developed symptoms in other parts of your body besides the affected part of your skin – see your GP and ask to be referred to an allergy specialist. If you suffered a small amount of swelling at the site of the sting there’s no need to be concerned. But a lot of swelling can be a sign that you’ve become allergic to the venom, so again see your GP for further advice. For more information on bites and stings.


There are several types of drug allergy, but if you experience a reaction such as a skin rash (hives), swelling or any other anaphylaxis symptoms, it’s important to get advice from a specialist through your GP. The following are the main drugs thought to cause severe allergies:

  • Antibiotics (if affected by one, you may also react to others within the same antibiotic ‘family’).

  • Anti-inflammatories, which include painkillers such as aspirin and ibuprofen, known as non-steroidal anti-inflammatory drugs (NSAIDs). If you have such an allergy, your GP may recommend paracetamol as a suitable painkiller, as experts believe those who are sensitive to NSAIDs can tolerate it.

  • Vaccines may cause problems with those who have an allergy to eggs, as some – including the annual flu vaccine – contain small amounts of egg protein.

  • Insulin, which is used to treat some people with diabetes, can trigger allergic reactions, but according to the Anaphylaxis Campaign, this is rare (viii).

  • General anaesthetics, which are administered during surgical procedures, can cause allergies, as can local anaesthetics. The most common cause of allergic reactions during general anaesthesia is a type of anaesthetic called neuromuscular blockers. Reactions to local anaesthetics are rare.


Found in a great many healthcare and other items, latex is thought to cause reactions in one to six percent of the UK population (ix). In the most severe form of allergy, the reaction is immediate and potentially life threatening. Other people may experience symptoms between six and 48 hours after exposure (in this case, the reaction isn’t usually life threatening). If you have relatives with allergies of any kind, you’re more likely to develop an allergy to latex than someone without family history of allergies. You’re also more likely to develop a latex allergy if you use latex gloves or other products containing latex on a regular basis. If you have a severe latex allergy, it’s crucial to avoid anything that contains latex. These include products such as rubber bands, condoms, washing up gloves, carpets, tyres, shoe soles, swimming caps, balloons, hot water bottles and erasers. Many different types of medical equipment also contain latex.

Anaphylaxis can be potentially life-threatening, but managing your risk daily, becoming as well informed about it as possible and planning ahead can help you lead an almost normal life. For more information on a range of allergies, as well as other common health conditions, visit our health library.


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Disclaimer: The information presented by Nature's Best is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications.



Our Author - Christine Morgan


Christine Morgan has been a freelance health and wellbeing journalist for almost 20 years, having written for numerous publications including the Daily Mirror, S Magazine, Top Sante, Healthy, Woman & Home, Zest, Allergy, Healthy Times and Pregnancy & Birth; she has also edited several titles such as Women’ Health, Shine’s Real Health & Beauty and All About Health.

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