The different ways the immune system defends the body are complex and sophisticated.

One of its activities is to produce antibodies. Their job is to neutralise intruders, or so-called antigens.

Most of the time, these immunological reactions are good for us. But sometimes the immune system over-reacts and massively defends against something that poses no real threat.

These harmful over-reactions are called hypersensitivity or allergy.

Although the immune system reacts to allergens in essentially the same way, the resulting allergies can be quite varied.

Symptoms show themselves in different ways (e.g. sneezing, coughing, itching, rash), on different parts of the body (e.g. eyes, nose, skin, lungs), and with different degrees of severity.