Immune system

When your body overreacts to a substance in your environment. Severe reactions are called anaphylaxis and are life threatening.

A fever is when your body temperature is above 38.0C. It is a normal part of your body's response to infection. Although it can be uncomfortable, most healthy adults can tolerate a fever well. A fever is also a sign you could be spread infection to others.

HIV is a virus that damages the cells in your immune system and weakens its ability to fight everyday infections and diseases.

When your body mistakenly uses its immune system to attack the area between your joints. Rheumatoid and psoriatic arthritis are forms of inflammatory arthritis.

You develop type 1 diabetes if your body is not creating enough insulin to keep blood glucose (sugar) levels in the normal range. High blood glucose can cause damage to your body over time.