Snot is a secretion from the nasal cavity. Most people with a cold will constantly have a runny nose; some people also have a runny nose when eating hot or spicy food; and some people, when they are emotionally excited, usually have a runny nose and tears at the same time. So, why do people have a runny nose? In normal people, the glands in the nasal mucosa secrete about 1,000 milliliters of mucus every day to replenish the water lost by the respiratory airflow and maintain the humidity of the nasal mucosa. The mucus, like a blanket, covers the cilia on the surface of the respiratory mucosa, adhering to bacteria, viruses, dust, etc. in the air. Relying on the directed movement of the cilia, the "mucus blanket" is sent to the nasopharynx and swallowed or spat out unconsciously. This is a natural physiological process that doesn't need special attention. When people have a cold, due to the abnormal stimulation of the nasal mucosa, the secretions increase significantly, and the cilia's activity is also affected, causing the mucus to accumulate and not be discharged in time, so it overflows from the nostrils. When some people eat hot or spicy food, the heat or spicy smell also stimulates the nasal mucosa, making the sensory nerve endings in the nose excited, prompting the glands to secrete excessively, resulting in a runny nose, and in severe cases, even tears and snot flowing together. This is because the lacrimal glands and nasal glands are controlled by the parasympathetic nerves in the autonomic nervous system, and the nasolacrimal duct is connected to the nasal cavity, so snot and tears will flow together.
A runny nose that always occurs and needs to be wiped off frequently is not only uncomfortable, but also troublesome and unsightly, which is annoying. A large amount of purulent snot flowing back for a long time can easily lead to infections of the lower respiratory tract and digestive tract, so it's better to treat it as soon as possible.
In the diagnosis of nasal diseases, snot also has great value. Doctors can make a preliminary diagnosis and appropriate treatment based on the characteristics and changes of snot. For example, if there are frequent sneezing and a large amount of clear watery snot, it is likely that the patient suffers from allergic rhinitis; from the clue of continuous suction of bloody snot, nasopharyngeal cancer can be detected early; when encountering a side of foul-smelling purulent snot, it is necessary to check the teeth; according to the location of the purulent snot in the nasal cavity, it can be inferred that which sinus is inflamed; after sinusitis treatment, the color of the snot changes from yellow to white, and the consistency becomes thinner and the amount decreases, indicating that the inflammation is improving and there is hope for recovery.