Allergy

The immune system’s role is to attack anything that poses a threat to health, such as bacteria and viruses. During development, the immune system usually learns to ignore things that are harmless, such as food and pollen.

Some people, however, respond to harmless substances as if they were a threat, leading to a damaging immune response called an allergy. The substance that triggers the immune response is known as an allergen. People with a family history of allergy and asthma are at greater risk of developing allergies.

Common allergens include:

• Foods, for example peanuts, cow’s milk, eggs, shellfish
• Medicines, for example antibiotics
• Dust mites
• Pet urine, saliva or dead skin cells
• Pollen
• Insects
• Ticks
• Moulds

During an allergic response, the immune system produces a protein called immunoglobulin E (IgE). The IgE binds to specialised immune cells called mast cells, triggering the release of chemicals such as histamine that cause allergy signs and symptoms.

Coeliac disease is sometimes referred to as a gluten or wheat allergy, but it is not IgE-mediated and instead involves different parts of the immune system.

The symptoms of an allergy vary depending on the type of allergen and the way a person is exposed to it. Symptoms usually develop within a few minutes of exposure and can include:

• Hay fever – runny nose, sneezing
• Conjunctivitis – red, watery, itchy eyes
• Eczema – dry skin
• Hives – a raised, red, itchy skin rash
• Dermatitis – red, itchy skin
• Vomiting, stomach cramp, diarrhoea
• Asthma – wheezing, chest tightness, difficulty breathing

The most severe form of allergy is a generalised reaction called anaphylaxis, which is life-threatening and requires emergency attention.

Some people experience recurring, itchy hives but can’t identify what they are allergic to. Our researchers discovered that this condition, known as chronic spontaneous urticaria, is caused by an aberrant autoimmune response directed at IgE receptors on mast cells in the skin. The researchers are now investigating whether the autoimmune response could be switched off by new, targeted treatments.

Childhood food allergies are very common in Australia, affecting 10 per cent of children under one year old. Common triggers in childhood include egg, peanuts, tree nuts and cow’s milk. Many children will outgrow their allergies, but others remain affected for life.

The number of children affected by food allergy has risen over recent decades. The causes driving this trend are complex and poorly understood.

Our researchers are part of a large infant health study aimed at understanding how allergies develop. They have found that some babies are already primed for allergic disease by the time they are born. These babies display hyperactive immune cells linked to the development of food allergies. Our researchers are now studying why some babies have these hyperactive immune cells, in work that could lead to future treatments to prevent food allergies.

Allergies are managed in several ways:

• Avoidance of the allergen, for example by not eating certain foods.
• Medications such as anti-histamines and corticosteroids to reduce symptoms during a mild allergic response.
• Administration of adrenalin (often via an autoinjector) to counteract an anaphylactic reaction.
• Immunotherapy, a form of vaccination, that can sometimes reduce sensitivity to particular allergens such as pollens, dust mites and bee venom.

Institute researchers are not able to provide specific medical advice to individuals. For further information, please visit ASCIA.