Dry air is another cause of cold and flu. This is the reason why cold is more common in the winter season. The inhaling of dry air leads to drying of the mucus membranes which protect us against viral attacks.

Though fatigue is not a cause of cold, if proper rest is not taken it recovery from cold or flu might be prolonged.

Cigarette smoking is another cause of cold. This is because smoking leads to irritation of the nasal airways and thus increases vulnerability to cold and flu infection. Passive smokers are also susceptible to cold and flu infection.

Some allergies lead to inflammation of the nasal passage lining and thus cause cold and flu. The allergic reactions which cause inflammation of the nasal passage are termed as allergic rhinitis.

Another cause of cold and flu is unhygienic lifestyle. Adopting hygienic measures is the best protection against cold and flu. Ensure that you wash your hands after you exercise, go out for shopping, return from office etc. Washing of hands destroys any virus you might have acquired. Mouth and nose should always be covered while sneezing and coughing. You should never touch your eyes, nose or mouth when you are with someone suffering from cold or flu.

The immune system protects the body from viruses and infectious diseases. As soon as the cold or flu virus enters the body the immune system tries to fight it by producing mucus and inflaming the blood vessels. People with strong immune system either do not get cold or they recover from it easily. People whose immune systems are compromised, like pregnant women, children, patients suffering from cancer, patients suffering from asthma etc, are not able to fight the virus easily and they, at times, acquire viral pneumonia.

It is a common notion that cold weather causes cold and flu. But cold weather is not the cause of cold and flu. The fact is that during the winter season people prefer staying indoors and in close proximity to each other. This makes a way for the virus to get transmitted easily. This is the reason why children are more susceptible to cold and flu as they are always in the proximity to other children in schools and playgrounds. Another reason for the spreading of cold in winter is that during this season the mucosa of the nasal passage dry up due to central heating. The mucosa is the body’s mechanism to defend against viruses and infections. So, when the mucosa dry up people become vulnerable to cold and flu.

Cold and flu are contagious. The viruses are transmitted through air when an affected person coughs or sneezes. The viruses can also spread when a healthy person is contaminated by the infected secretions. Cold and flu viruses can also live on things like books, door knobs, keyboards etc and when a healthy person touches these objects, he/she gets infected too.

The main cause of cold and flu is a viral infection. Approximately 30% to 35% of cold and flu infections are caused due to rhinovirus. Other common viruses causing the ailment are coronavirus, syncytial virus, and denovirus virus. However, as stated earlier, there are more than 200 viruses that can cause cold and flu.