1. Getting under 5 hours of sleep a night has been shown to greatly depress immune function in your body.

2. In your blood, there are around 50 billion white cells whose only interest is to keep your body's natural defences in good condition !!!

3. When the immune system attacks a harmless substance or chemical in the body, it leads to an allergic reaction.

4. There are four phases of an immune response: recognition, amplification of defense, attack and suppression.

5. Some sunlight helps the body produce vitamin D and too much sunlight suppresses the immune system.