Immune systems are god’s gift to the human body to fight against the thousands of infections that are possible to occur every day if we do not have this protection. When a person is fit and healthy and eats a healthy meal every day his immune system would remain powerful. Lack of sleep, excessive drinking of alcoholic beverages, smoking and excessive exposure to extreme temperatures, reduce the strength of the immune system. When the immune system is weak the body is weak to fight off any infections and so it is quite easy to fall sick. This is the reason why Doctors advise every one to maintain a good lifestyle to improve the immune system’s strength.