By Adam Collison, Elizabeth Percival,Joerg Mattes, and Rani Bhatia of theUniversity of Newcastle. This story was originally published by The Conversation.
Allergies are reactions caused by the immune system as it responds to environmental substances that are usually harmless to most people. They may occur in response to a range of different material (called allergens), such as food, pollen, dust mites, animals, insect stings, or medicines.
An allergy can affect different parts of the body. Allergic rhinitis, or hay fever, for instance, affects the nose and eyes, while eczema affects the skin. Food allergies affect the gut, skin, airways, lungs, and sometimes the entire body through the blood vessels.
Other conditions such as asthma, which affects the lungs, and eosinophilic oesophagitis, which affects the tube from the throat to the stomach, are closely related to allergy. But they have slightly different underlying causes.
A range of reactions
While most reactions are only mild to moderate in severity (and can be treated with antihistamines), some can be life-threatening and require emergency medical treatment. The most severe, systemic allergic reactions are ...