Normally, your body’s immune system protects you against infection and diseases. Allergy is caused by your immune system overreacting to usually harmless substances from, for example, grass, house dust mites, animal hair or certain foods. Substances like these that trigger an allergic reaction are known as allergens. They may cause a reaction through being inhaled (breathed in), eaten, or simply touched.
Allergy is an increasing health problem
Allergy is a health problem that is becoming more and more common worldwide. It is estimated that around a quarter of all people in Europe suffer from respiratory allergy (allergy that affects breathing and the airways), and half of these people are allergic to grass pollen. Consequently, allergy is is one of the most common reasons why people visit their doctor.