Causes of Allergy

The substances that cause an allergic reaction in sensitised people are known as allergens, and they can enter the body in a variety of ways:

• Inhaled into the nose and the lungs
  Examples are: airborne pollens of certain trees, grasses and weeds, dust mite droppings, mould spores, cat and dog dander
• Ingested by mouth
  These are generally the things that we eat and drink, for example peanuts and some medicines
• Injected
  Reactions to stinging insects and injectable drugs
• Absorbed through the skin
  Things we come into contact with, such as stinging nettles, poison ivy and cosmetics

In sensitised people these substances are considered foreign by the body and the normal reaction of our body to any type of invasion by foreign substances is to defend itself. This is the role of our immune system.