Sneezing, sore throat, runny nose - everyone knows the first unpleasant signs of a cold. Why do we catch colds so easily? What terrible diseases can masquerade as a common cold? Is it possible and how to prevent and cure colds without medications? When will home remedies help and when should you see a doctor immediately? How to protect children from colds? You will find answers to these and many other questions in this book. You will learn about the human immune system and natural ways to train it: hardening, physical exercise, exposure to natural factors, proper nutrition. And also about how to resist viral infections, organize proper nutrition during illness and significantly improve the quality of life. The detailed classification and diagnostic methods proposed by the author will help you in each specific case to determine the possible causes of the disease and methods of its treatment.