The power of our body to fight against various disease producing agents is known as defence mechanism. This defence mechanism depends upon various factors which can be categorised mainly into two types-common factors and special factors.
Amongst the common factors, the most important is the health of human beings. For keeping good health, one should take a nutritious balanced diet. A balanced diet is that which contains carbohydrates, fat, proteins, vitamins in proportionate amount.
The skin saves us against many micro-organisms producing diseases, provided that it is intact. In case there are cuts or abrasions on it, the micro-organisms penetrate the body through those cuts and abrasions and can cause diseases. Therefore, a cut or an abrasion should never be left open. In case there is no bandage available, it may be covered by a clean cloth.
Some bacteria reside on and inside the human body. They do not cause any disease and by their presence they do not allow disease-causing organisms to settle on those places. The human body secretes a variety of fluids, which are killers for disease causing micro-organisms. For instance, gastric juice (acidic in nature) secreted by our intestinal tract kills all organisms which enter our body through food.
There are a few automatic activities of our body known as 'reflex phenomenon or action', which protects the body against many infections. This reflex phenomenon includes sneezing, coughing and vomiting.
Fever is one of the most important constituents of the defence mechanism of our body. The organ which regulates the temperature of our body is known as hypothalamus and is situated in the brain. When micro-organisms after entering the body release toxic products and these reach the brain through blood, the hypothalamus starts increasing the temperature of the body and the person gets fever.
This fever is very useful for the human body because due to the increase of temperature, the micro-organisms which are the root cause of the problem get killed. We are living in an environment which is full of bacteria. Many of these bacteria can produce serious diseases, but all of us do not suffer from such diseases. It is due to a special power present in our body to fight these diseases, known as innate immunity.
In a nutshell, we can say that since nature has provided us with defence mechanism to fight against so many diseases, let us maintain it or rather increase it by way of immunisation.