The common cold seems to worsen at nighttime, and the symptoms are noticed more clearly during the night. This is probably because the daytime activities available vary less during the night to divert the attention of the person from experiencing inconveniences and problems. There are a few elements that influence the increase of symptoms of colds at night times. One of these factors which are responsible for the cause of discomfort at nighttime is that the body is kept in a horizontal position rather than in a vertical position. When the person is performing his duties normally during the daytime, the standing posture or sitting posture will distribute the gravity and pressure equally all over the body. But when the body is lying down, the pressure is distributed in different way which offers an additional pressure on the sinus cavities.
This excess pressure that is created on the sinus cavities is known to enhance the measure of discomfort or inconvenience that is felt by the person suffering from a cold. The circadian rhythms are natural rhythms in the body which show an impact on the hormone synthesis depending on the time of the day. The hormones that are responsible for generating antibodies in order to fight with fevers and infections are found to be produced during the daytime hours. The hormones are less active during the nighttime. Hence, the defense mechanisms in general are weaker during the nights, and the cold symptom severity becomes high. These hormones during the day are supposed to enhance the production of white blood cells. This increase in white blood cells in the blood is responsible for increasing the defenses in the human body. So the cold symptoms are more severe in the nighttime .
The temperature that is present outside will be colder during the night, and the person becomes very tired after carrying out the various activities in the daytime. Hence, he will be less energetic to be able to fight against the cold at nighttime than during the daytime.