Anaphylaxis

What is anaphylaxis?#

Anaphylaxis is the most severe type of allergic reaction and is a medical emergency. Within minutes of exposure to the allergen, or “trigger”, a person can develop life-threatening symptoms involving their breathing and/or their heart.

An allergy occurs when the immune system overreacts to a substance in the environment that is harmless for most people. This trigger is called an allergen. The immune system responds by making an antibody to attack the allergen, which sets off a chain of immune reactions. Allergies can be mild, moderate or severe.

Hospital admissions for anaphylaxis have risen sharply over recent decades, and anaphylaxis from food allergy in particular has become more common.

Signs and symptoms#

Anaphylaxis usually develops within about 20 minutes to 2 hours after exposure to the allergen. Symptoms may be mild at first but can get worse very quickly. A small number of people develop a severe reaction with no earlier signs of a mild or moderate reaction.

Mild to moderate allergic reaction#

• Swelling of the lips, face and eyes
• Hives or welts on the skin
• Tingling mouth
• Abdominal pain or vomiting (for an insect allergy, these can be signs of anaphylaxis)

Severe allergic reaction (anaphylaxis)#

• Difficult or noisy breathing
• Swelling of the tongue
• Swelling or tightness in the throat
• Difficulty talking, or a hoarse voice
• Wheeze or persistent cough
• Persistent dizziness or collapse
• Becoming pale and floppy (in young children)

Common triggers#

Almost any food can be a trigger, but a small number of foods account for the large majority of allergic reactions: shellfish, fish, eggs, milk, wheat, peanuts, tree nuts, sesame and soy. Other common triggers include:

• Insect bites and stings, such as from bees, wasps and stinging ants; ticks can also trigger anaphylaxis
• Medicines, including some prescription drugs (such as penicillin), over-the-counter medicines (such as aspirin) and herbal preparations

Less common triggers include exercise, anesthetic drugs and latex. Sometimes, despite investigation, a person’s trigger cannot be identified; these are called “unknown triggers”.

Factors that can increase the risk or severity#

• Poorly controlled asthma
• Exercise
• Alcohol
• Fatigue (tiredness)
• Posture — standing and walking
• Hormonal changes (for example, around menstruation)
• The amount of food eaten and how it is prepared (in people with food allergy)
• Taking a non-steroidal anti-inflammatory medicine such as aspirin or ibuprofen

Emergency first aid for anaphylaxis#

Anaphylaxis is a medical emergency. Follow the person’s individual anaphylaxis action plan if they have one:

• Lay the person flat. Do not let them stand or walk.
• Give the adrenaline (epinephrine) injector.
• Call your local emergency number (for example 911 in the US and Canada, 112 across the EU and many countries, 999 in the UK, or 000 in Australia) for an ambulance.
• Phone the person’s family or emergency contact.
• A further dose of adrenaline may be given if there is no improvement after 5 minutes.
• Transfer the person to hospital for at least 4 hours of observation.

For someone with known asthma and severe allergy to a food, insect or medication who has sudden breathing difficulty, always give the adrenaline injector first and then the asthma reliever puffer, even if there are no skin signs such as hives or welts. If the person is unresponsive and not breathing normally at any time, begin CPR.

Adrenaline is the first line treatment#

Adrenaline works fast to reverse a severe reaction. It is injected into the muscle of the outer mid-thigh — midway between the knee and hip joints, on the outer side of the thigh — using an adrenaline injector. These devices, such as EpiPen® and Anapen®, are designed to be used by people who are not medically trained and deliver a single pre-measured dose.

Different strengths are available according to weight, for example:

• A junior strength (such as EpiPen® Jr or Anapen® 150) for children who weigh between about 7.5 kg and 20 kg
• A standard strength (such as EpiPen® or Anapen® 300) for children over about 20 kg and for adults
• A higher strength (such as Anapen® 500) for children and adults over about 50 kg

Your treating doctor or pharmacist will give you detailed instructions on how to use your injector. Once you are diagnosed as being at risk of anaphylaxis, always carry your adrenaline injector(s) and your action plan, which is completed and signed by your doctor or nurse practitioner.

Diagnosis#

If you are thought to be at risk of anaphylaxis, or you have anaphylaxis for the first time, your doctor will record the history of your reaction and suspected triggers and refer you to a clinical immunology or allergy specialist. The specialist will make a diagnosis and advise on prevention and emergency treatment.

To make a diagnosis, the specialist will:

• Take a detailed medical history, including questions about what led up to the reaction
• Perform a physical examination
• Arrange investigations, which may include blood tests to measure allergen-specific antibodies (immunoglobulin E, or IgE), skin prick tests to confirm or rule out suspected triggers, and tests to exclude other conditions that can look like an allergic reaction

Beware unproven allergy tests#

Some “tests” that claim to diagnose allergies are not scientifically or medically proven. Relying on an unproven test can be dangerous: it may mean you do not get the medical attention you need, delay an accurate diagnosis, be expensive, and lead to unnecessary dietary and lifestyle restrictions. Methods that are not proven and may lead to inappropriate treatment include Vega testing, Alcat testing, cytotoxic food testing, kinesiology, hair or stool analysis, IgG antibody testing to food, iridology, pulse testing, reflexology and Rinkel’s intradermal testing.

Management#

There is currently no cure for allergy, so management focuses on avoiding triggers and being prepared. Your specialist will discuss how to prevent reactions and how to manage one, including completing an anaphylaxis action plan and teaching you how to use an adrenaline injector if one is prescribed.

Not everyone with a food, insect or other allergy is prescribed an adrenaline injector; the specialist will assess each person’s level of risk. People with a medication allergy are generally not prescribed an injector, as the trigger is usually easier to avoid than a food or insect. You will need regular follow-up visits with your specialist. For food allergy, advice from an experienced food allergy dietitian may also help.

Preventing anaphylaxis#

Avoiding all known triggers is the most important strategy. Other recommendations include:

• Tell people about your allergy. Let your workplace know, and make sure a few colleagues know where your emergency medication is kept and how to give it to you.
• If you have a medication allergy, always tell every treating doctor and pharmacist.
• Wear a medical identification bracelet so that, if you lose consciousness, ambulance and hospital staff know about your condition.
• If you have a food allergy, always read food labels and tell staff about your allergy when eating out, and take extra precautions when eating out or traveling.
• If your food allergy is hard to manage, or you have several food allergies, consider seeing a specialized food allergy dietitian.
• If you have an insect allergy, be aware of environments that raise the risk of a sting or bite and do what you can to minimize exposure.

Children with severe allergies#

• Educate your child in a way that suits their age and understanding. For a food allergy, stress only accepting food from trusted adults such as parents or caregivers, never sharing food, and washing hands before and after eating.
• Tell the childcare service, kindergarten, school and other carers about your child’s severe allergy.
• Give the organization a current copy of your child’s action plan, including a recent photograph, and provide at least one in-date adrenaline injector so a management plan can be put in place.

Long-term outlook#

Most children grow out of allergies to milk, egg, wheat and soy. However, allergies to peanut, tree nuts, sesame and seafood are usually lifelong. People who have had anaphylaxis from an insect allergy should ask their specialist whether immunotherapy (desensitization) is available and suitable for them.

Anaphylaxis first aid training is widely available for the community — including parents, friends, carers, colleagues, students and club members — as well as for schools, children’s education and care settings, and food businesses.

Key points#

• Anaphylaxis is a severe, life-threatening allergic reaction and a medical emergency.
• The best prevention is to avoid whatever causes the reaction.
• Symptoms may be mild at first but can worsen very quickly, usually within 20 minutes to 2 hours of exposure.
• Adrenaline injected into the outer mid-thigh is the first line treatment: lay the person flat, give adrenaline, and call for an ambulance.
• Be wary of unproven allergy tests, and see a clinical immunology or allergy specialist for diagnosis and an action plan.

Where to get help and trusted information#

For evidence-based global health guidance, see Source: World Health Organization (WHO).