The well known verse which says, “The prime cause for all Colds is Germs” is only partially true. The far more important cause in respect to Colds is Reduced Body Resistance OR what we say Weak Immunity. So it is very right to say that: it is the exposure to an unclean environment containing disease germs, combined with lowered body resistance, is what that produces the usual cold.

In foul or polluted air, different forms of germs are present – many of them absolutely harmless, like the yeasts, the moulds, the germs that sour milk, and the germs that are responsible for decay of dead plants and animals. But among them there are many which attack the human body and are responsible for many infectious diseases.

These various forms of germs are always present in every environment (though their percentage varies), in nose and in throat. These germs never pose any problem until the body resistance, in some way, is lowered. This is not meant to say that if you are the owner of great health and vigor, you should not care about the environment in which you live. This only means that if anyhow, because of some reason, you have to spend some time in such an environment, and you own a great health, then no need to worry much about it. The people, who know about hygiene, are very well familiar with the fact that “Cleanliness is the Second name of GOD”

Other Reasons responsible for Colds

• Exposure to Strong drafts: It is exposure to a strong draft plus presence of germs and a reduced body resistance which produces the usual cold. It is never advisable to sit in a strong draft during perspiration, even if you are healthy.
• Living in Foul of Stuffy Rooms: The people, who live in foul or stuffy rooms, are prone to get the infectious diseases. Why? Because, it is almost certain that such air contain these germs in enormous amount. Then these diseases spread from one person to another; they spread through families, schools and shops etc.
• Obstruction in Nose: Many people are susceptible to colds due to abnormalities in their nose or throat. Nasal obstruction is a very general condition. These obstructions are often caused by adenoids in childhood, which pose interference in proper development of the internal nasal structures. Malformation of the teeth and dental arches in childhood are common causes of nasal obstruction. Such malformations are generally caused by the arresting of the growth of the upper jaw and nasal structures. Such conditions not only predispose to colds, but enhance their severity and the danger of complicating infection of the bony cavities in the skull that communicate with the nose.
• Unhealthy Skin: It is very familiar fact that exposure to chilling air often causes colds. This is usually because the nerve centers controlling the blood circulation of the skin are over-sensitive. And due to this they exhibit a reaction when exposed to chills, causing a disturbance in the blood circulation, and of the heat-regulating machinery of the body, which produces colds. 
• Constipation: Constipation also influences colds. Thus it should be vigorously combated by exercise in the open air, sound sleep, improved fresh air circulation in bedrooms, with plenty of nourishing food, including plenty of green vegetables and fresh fruits.
• Overeating: Overeating often leads to nasal congestion, and obstruction in nose make you more susceptible to catch colds.