Anaphylaxis

3. Medical information about anaphylaxis

What is an allergic reaction?

Allergy occurs when a person's immune system reacts to substances in the environment that are harmless for most people. These substances are known as allergens and are found in house dust mites, pets, pollen, insects, moulds, foods and some medicines.

What is anaphylaxis?

Anaphylaxis is a severe, rapidly progressive allergic reaction that is life threatening. Allergic reactions, including severe life-threatening allergic reactions (anaphylaxis) are becoming more common in children. Deaths are less common, however, deaths do occur and anaphylaxis must therefore be regarded by schools as a medical emergency requiring a rapid response.

Please note that any student with a diagnosed allergy is at higher risk of their condition progressing to anaphylaxis and should be monitored carefully.

What are the main causes?

Research shows that students in the 10 to 18 year age group are at greatest risk of suffering a fatal anaphylactic reaction¹. Certain foods and insect stings are the most common causes of anaphylaxis. 9 foods cause 95% of food-induced allergic reactions, including anaphylaxis, in Australia:

• peanuts
• tree nuts (for example, hazelnuts, cashews, almonds, walnuts, pistachios, macadamias, brazil nuts, pecans, chestnuts and pine nuts)
• eggs
• cow's milk
• wheat
• soy
• fish
• shellfish (for example, oysters, lobsters, clams, mussels, shrimps, crabs and prawns)
• sesame seeds.

Other common allergens include some insect stings, particularly bee stings but also wasp and jumper jack ant stings, tick bites, some medications (for example, antibiotics and anaesthetic drugs) and latex.

Signs and symptoms

Mild to moderate allergic reaction can include:

• swelling of the lips, face and eyes
• hives or welts
• tingling mouth
• abdominal pain and/or vomiting (these are signs of a severe allergic reaction in the case of insect allergy).

Anaphylaxis (severe allergic reaction) can include:

• difficult/noisy breathing
• swelling of tongue
• swelling/tightness in throat
• difficulty talking and/or hoarse voice
• wheeze or persistent cough
• persistent dizziness or collapse
• pale and floppy (young children)
• abdominal pain and/or vomiting are signs of a severe allergic reaction to insects.

Symptoms usually develop within ten minutes and up to two hours after exposure to an allergen, but can appear within a few minutes.

Treatment of anaphylaxis

Adrenaline given as an injection into the muscle of the outer mid-thigh is the first aid treatment for anaphylaxis.

Individuals diagnosed as being at risk of anaphylaxis are prescribed an adrenaline autoinjector for use in an emergency. Currently, the only available brand of adrenaline autoinjector in Australia is EpiPen. The EpiPen is prescribed for those weighing over 20 kg. The EpiPen Jr contains a smaller dose of adrenaline and is prescribed for those weighing 10 to 20 kg. These adrenaline autoinjectors are designed so that anyone can use them in an emergency.

¹WK Liew, E Williamson, MLK Tang. Anaphylaxis fatalities and admissions in Australia. Department of Allergy and Immunology 2009; 123: 434-442