A cold is a viral infectious disease of the upper respiratory tract. It occurs throughout the year. Some of the viruses that cause the common colds are seasonal, occurring more frequently during cold or wet weather. Infection occurs when the immune system is weakened and in our respiratory system enters a virus in sufficient quantity. To catch a cold there must be several factors that are in favor of viruses. A strong immune system will prevent the infection of the virus. Our immune system stops the virus and protects our organism from bursting an inflammation. Therefore, it is highly important to take care of our health and to boost up the immune system.