What is anaphylaxis?

Anaphylaxis is a severe allergic reaction, typically to food, insect stings, medicine or latex. It can happen in minutes and be life-threatening if it isn't contained. To do that, you need to spot the early signs, administer the right treatment and seek urgent medical attention. ¹

Up to 5% of people are likely to be affected by anaphylaxis at some point in their lives, according to the World Allergy Organization.¹ It’s not just your particular allergy trigger that can increase the risk of it happening. Having anaphylaxis once makes it more likely in the future.² Symptoms are mild to moderate in most instances and death is rare.^1,3 But doctors can’t predict how any individual reaction will progress. So it’s vital to be prepared.¹

Read on to find out about anaphylaxis: What causes it, including common allergy triggers; typical anaphylactic symptoms, including in kids; and what to do if you spot them. The article looks at emergency medication. We also suggest tips for living with the risk of anaphylaxis after diagnosis and look at whether there’s a cure. 

What is the first aid for anaphylaxis?

This is how to help someone else but the steps are the same if you have a sudden and potentially life-threatening allergic reaction.^1,3

1.  If an adrenaline nasal spray or auto-injector is to hand, give the first dose.⁴ The instructions are usually on the side and shots work through clothing.⁵ Also note the time.

2. Call 999 and say you think it’s anaphylaxis. The person may be wearing an allergy alert bracelet giving life-saving information. Share that too. 

3. Lie them down flat with their feet raised. Unless they’re pregnant when they need to be on their left side instead. If breathless, stay semi-upright. Someone who’s unconscious needs to be in the recovery position (also lying on their side, head tipped back slightly). 

4. Wait 5 to 15 minutes. If the symptoms haven’t improved, and the ambulance hasn’t arrived yet, give a second dose of adrenaline.

5. Be ready to perform CPR if the person goes into cardiac arrest and you know how.

6. When the paramedics take over, hand them the used adrenaline device so they know what medication the person has had already.

What are anaphylaxis signs and symptoms? ^1,5

An anaphylactic reaction typically starts seconds or minutes after you meet your trigger, although it can be several hours later. ^1,2  It can cause any of these signs and symptoms, some of which might be more severe than others: ⁶

• Skin reactions, such as hives, itching, flushing or paleness
• Swollen tongue or throat
• Wheezing and difficulty breathing
• Nausea, vomiting or diarrhoea
• Weak or rapid pulse
• Drop in blood pressure (hypotension) and shock
• Dizziness or fainting
• Sense of impending doom

Your symptoms could feel different next time, if you were to have anaphylactic reaction again.⁶

What is the difference between anaphylaxis and anaphylactic shock?

Anaphylaxis is the exaggerated reaction, usually allergic, from your immune system.¹ Anaphylactic shock is what can happen if this reaction progresses to cause a sudden fall in blood pressure.⁶ Vital organs then can’t get enough oxygen and nutrients, which can be damaging or fatal without immediate treatment.⁷ 

The risk of anaphylactic shock is a good reason to carry emergency medicine at all times and wear a medical alert bracelet.

Why does anaphylaxis happen: Causes and triggers?

Anaphylaxis is the result of an overactive immune system.¹⁰ It’s an allergic reaction, like hay fever, except that this is systemic and severe.^10,11 That is, certain allergens can trigger a more intense immune response that spreads from where the contact happened to affect your whole body.¹¹

During an allergic reaction cells release chemicals like histamine to help get rid of the allergen from your body.¹⁰ That typically causes local symptoms, like the runny nose some people get after breathing in pollen.^10,12  Anaphylaxis mobilises many more cells and these can act on your airways, breathing and circulation.^1,11

Anaphylaxis has other causes apart from allergies. Factors like exercise may also play a part.¹ Idiopathic anaphylaxis is when it’s not clear why the reaction happened. ¹ 

Which allergies can trigger anaphylactic reactions?

Anaphylaxis is much more common with certain allergy triggers. Children and teenagers are most at risk from food and insect stings; for adults, it’s stings and medicine.¹³ A tiny amount of allergen may be all it takes but the risk increases with greater exposure.^3,14   

Let’s look at food, insect venom, drug and latex allergies in more detail.

Food allergy and anaphylaxis

Hen’s egg, cow’s milk, wheat and peanut are the most common causes of food-related anaphylaxis in children.¹ With adults it varies depending on the local diet but these are some of the usual suspects: peanuts, tree nuts, seeds like sesame, wheat and shellfish.¹ 

Sometimes the food allergy needs a co-factor to activate it and cause a severe reaction. That could be taking aspirin shortly after eating, extreme cold, stress, drinking alcohol with food, premenstrual hormone changes or exercise (see below).^1,15 Alpha-gal syndrome is a rare allergy to lamb, pork, beef and venison that develops after a tick bite. It can cause delayed anaphylaxis, starting 4-8 hours after a meal.¹⁶

It’s also possible to have an anaphylactic reaction to lipid transfer proteins in plant-based foods, from nuts to apples, grapes, dried fruit and tomatoes.¹⁷

Insect venom allergy and anaphylaxis

Adults are 3 times more likely than kids to experience anaphylaxis from bee, wasp, yellow jacket or hornet venom. A large local reaction can be an advance warning. Around 5% to 15% of people have a systemic or anaphylactic reaction next time they’re stung.¹⁸

Drug allergy and anaphylaxis

People in hospital seem to be more vulnerable to drug allergy-related anaphylaxis - and the elderly are more likely to die from it.² Among the more common triggers are antibiotics like penicillin, muscle relaxants used in general anaesthetics, and insulin for treating diabetes.^1,2 

Allergy immunotherapy can cause anaphylactic reactions too.¹³ That’s why all allergy immunotherapy injections and some doses of other forms of the treatment take place at the clinic. 

Latex allergy and anaphylaxis

Latex allergy particularly affects healthcare workers who use medical gloves and it’s relatively rare for it to cause anaphylaxis.⁶ Certain medical equipment, rubber bands, balloons and condoms can contain latex too.¹⁹ Notify the doctor, dentist, school and caregivers if you or your child are allergic to natural rubber.

What else can cause anaphylaxis?

Blood transfusions can lead to a different type of immune response that may trigger anaphylaxis. Sometimes the immune system isn’t thought to be involved at all, for instance in severe reactions to certain chemicals and medicines including aspirin.⁹ 

Aspirin is a non-steroidal anti-inflammatory drug and other NSAIDs can also cause anaphylaxis. So can some opioids, chemotherapy drugs and contrast agents, which are substances you might be given before an MRI scan and other medical imaging exams.^1,9 And certain sulphites used to preserve food.⁹

How is exercise linked to anaphylaxis?

It’s rare but physical activity can cause anaphylaxis on its own or as a co-factor with something else, like taking aspirin or another NSAID. You might be allergic to a food like wheat or shellfish but have no symptoms unless you exercise a few minutes or even hours after eating.^1,9,15 

Food-dependent exercise-induced anaphylaxis (FDEIA) is more common in women under 30.⁹ And studies suggest it could also happen if you exercise first. ^1,9,15

Can children have anaphylaxis?

Yes, and it can happen at any age from babies on their first solid foods to school-age kids and teenagers. Anaphylaxis seems to affect more boys than girls. And 92% of kids get skin symptoms as part of the reaction (Anaphylaxis in Children and Adolescents: The European Anaphylaxis Registry, 2016).²⁰

Babies and infants

Most new cases of anaphylaxis in kids are diagnosed before the age of 4.²¹ Skin rashes, coughing and stomach issues, particularly vomiting, are common.²⁰ Other signs can be subtle in young children; hands in mouth or pulling their ear, drowsiness, slurring or a squeaky voice.^20,22

School-age kids

Parents rightly worry about protecting their allergic child at school but anaphylaxis still mostly happens at home – that’s over a third of cases. At this age, kids begin to develop allergies to bee and wasp stings. And parks, gardens and the countryside become higher risk places.²⁰ 

Teenagers

Fatal allergic reactions to food are most common among adolescents and young adults. Teenagers are starting to manage their own medication, want to fit in socially and are more prone to taking risks.² They report having trouble breathing or swallowing and display cardiovascular symptoms.²³

The most frequent cardiovascular symptoms in teens are dizziness and a sudden drop in blood pressure leading to collapse.²⁰

How do you get an anaphylaxis diagnosis?

An anaphylactic reaction is often diagnosed in the emergency room, then confirmed by your doctor or allergy specialist in a follow-up assessment. Try to remember the circumstances and your anaphylaxis symptoms. The doctor will ask for your medical history too and may suggest allergy testing to help identify the trigger.

Risk factors to consider include:^2,13

• a family history of anaphylaxis
• having already had an anaphylactic reaction
• a history of asthma, especially if poorly controlled, or heart problems
• mastocytosis (an immune disorder)

Can allergy tests predict anaphylaxis?

No, but there is a blood test that may help assess your risk level. In allergy, the immune system reacts to proteins, some of which are known anaphylaxis triggers, for instance in peanut, tree nut and insect venom. The test checks whether you could be allergic to those specific proteins.²⁴ 

It’s called Precision Allergy Molecular Diagnosis (PAMD@).²⁴ Other types of allergy test include the skin prick test, regular blood test and challenge test.^1,2

What's the treatment for a potentially life-threatening allergic reaction?

The treatment for anaphylaxis is adrenaline, prescribed in a self-administered device for you to use in an emergency.¹ This can help reduce swelling, open up your airways and improve your blood pressure.^5,13 Around 10% of anaphylaxis episodes need more than one dose so always carry two devices.²⁵

Your doctor will explain how to administer the adrenaline and training devices are available.^1,5 Show your family in case you need their help.

Further treatment in the ambulance and in hospital could include oxygen, intravenous fluids and medications for specific symptoms.¹

Is there a cure for anaphylaxis?

Not yet but allergy immunotherapy may be able to lower the risk of a severe allergic reaction from peanut or Hymenoptera (bee and wasp) venom. The treatment aims to retrain your immune system with regular doses of the allergen until it becomes more tolerant.²⁶

Allergy immunotherapy isn’t suitable for everyone. Your GP or allergist can tell you more.

With drug allergy, desensitisation tends to be a short-term solution when there’s no alternative antibiotic or chemotherapy drug. It happens in hospital and if you stop taking the drug every day, then need it again, you’d have to repeat the process.²⁷

3 tips to help manage the risk of anaphylaxis

Your doctor will have lots of advice to share if you’ve had anaphylaxis or been diagnosed with an allergy that carries a higher risk of a severe systemic allergic reaction. Here are a few suggestions:

1.  Avoid your trigger: Read food labels and ask about ingredients when eating out. Be careful not to attract or provoke bees and wasps in sting season. Tell any healthcare professionals about your drug or latex allergy and make sure it’s in your records.

2. Look after your emergency medication: Make sure your adrenaline device is always in date and stored according to the instructions.⁹ Keep two doses with you at all times.⁶ Don’t be tempted to reach for antihistamine as it’s too slow and less effective for treating anaphylaxis.⁵ 

3. Have an action plan: Work with the doctor to create a personalized anaphylaxis action plan. Share it with your family, school or work and caregivers, so everyone knows what to do when and how to administer emergency medication.

The short version

Anaphylaxis is a life-threatening allergic reaction affecting your whole body. It needs immediate treatment with adrenaline. 

The severity of anaphylactic reactions can be minimized by recognising the symptoms early, having the proper medication available for self-treatment and seeking emergency medical care promptly.

Common causes of anaphylaxis include food, insect venom, medicine and latex allergies. A detailed blood test can help assess if you’re at risk, alongside your medical history and your family’s. Allergy immunotherapy may reduce that risk, depending on your trigger.