Hi, Thank you for your query. I can understand your concerns. Since water discharge is coming only from left nostril and to the extent it soaks up your night garment,CSF(cerebrospinal fluid) rhinorrhoea needs to be excluded in your case,though it a rare condition. Other common possibilty is excessive lacrimation from left eye irritation. Chronic sinusitis involving left paranasal sinus may also cause watery discharge or rhinorrhoea ,particularly any viral infection which often causes rhinorrhea on circadian rhythms. Cold temperature at night can also cause water discharge from nose ,even from one nostril.When air is exhaled, water vapor in breath condenses as the warm air meets the colder outside temperature near the nostrils. This causes an excess amount of water to build up inside nasal cavities. In these cases, the excess fluid usually spills out externally through the nostrils. Regards Dr. T.K. Biswas M.D. Mumbai