Colds and flu are not caused from cold weather, getting wet or chilled, or becoming overheated. However, those things, along with a combination of others factors, can lower one's resistance to colds and flu. Stress, allergies such as hay fever, poor nutrition, and fatigue from lack of sleep can all make one more susceptible to viruses that cause colds and flu. While colds and flu are not the same illness, they are caused by the same viruses. This is extremely difficult as there are more than 200 viruses causing colds and flu.
Some people have naturally high resistance to the viruses that cause colds and flu.
The rest of us can increase our immunity by washing our hands regularly, eating foods high in fruits and vegetables on a daily basis, avoiding extreme fatigue, controlling emotional stress, maintaining good personal hygiene, and avoiding cold, wet weather without adequate clothing. Colds and flu have similar symptoms, but flu symptoms usually have a more rapid onset, are more severe and last longer. It is important to closely monitor symptoms of both illnesses, as a severe cold may lead to a secondary infection in the middle ear or sinuses, and the flu can have potentially life-threatening complications, such as pneumonia. Colds and flu are most contagious during the first 24 - 48 hours after symptoms begin to appear. After exposure to cold and flu viruses, symptoms appear within one to three days, if they are going to appear at all.