The human body has an active immune system that aims to protect it from diseases such as infections and cancers. Sometimes, however, the immune system can be its own worst enemy. Allergies are one example of the immune system over-reacting to a perceived threat and causing more harm than good.
Common allergic conditions include:
Hayfever, with its a runny nose and/or itchy, watering eyes.
Eczema (also called atopic dermatitis), which is an itchy, dry skin rash.
Allergies, which can cause an all-over itchy red rash (hives) or life-threatening swelling (anaphylaxis).
Asthma, a complex condition that causes wheezing and difficulty breathing.