Our immune systems help us to keep healthy by protecting us from germs and other foreign bodies that could harm us. But some people's immune system doesn't work as well as others. In these people, when their bodies detect something that is normally harmless, their immune system overreacts. An allergic reaction can take many different forms. It may affect the skin, the ears, nose, throat and lungs and even digestion.

How do I know if I'm having an allergic reaction?

Just as there are many causes of allergy, there are also many different symptoms. An allergy caused by breathing in pollen or house dust mites may cause a runny nose and red, itching eyes (this is called hay fever or allergic rhinitis). Asthma may also be caused by breathing in certain allergens. Other allergies may cause itchy or bumby skin. Some  foods may also lead to skin reactions and digestive problems.

However, there are some allergic symptoms that may be a sign that a serious allergic reaction called anaphylaxis (anna-fill-AXE-is) is either about to happen, or could happen next time you react badly to an allergen.