If the symptoms of a cold are severe and even cause complications, they can cause certain harm to the body and even leave after-effects. If the symptoms of a cold are milder and do not cause serious harm to the body, they can even be beneficial to the body’s immune system. Because a mild cold is an invasion of related pathogens into the body, the immune system will recognize them and produce the appropriate antibodies. When a similar virus is encountered the next time, the immune system is able to recognize them quickly and repel them, which is how humans gain immunity to viruses. The vast majority of pathogens that attack the body are asymptomatic, called insidious infections, in which case the immune system acquires the appropriate immunity. When mild symptoms appear, the body still acquires some of the immunity, just as a nation’s army needs to go through drills and even wars to get better. The same is true for the immune system, which also needs to experience a variety of colds. There are some colds with mild symptoms and the vast majority of colds are insidious infections without any symptoms. Therefore, colds are good for the body’s immune system and immune capacity.