anesthesia
"Had a colonoscopy yesterday...went in feeling perfectly fine, woke up after procedure very congested and sneezing, with runny nose and watery eyes.  Sneezing continued all day, went through an entire box of tissues.  Took a dose of Benadryl before bed and woke up today perfectly fine.  After reading others' similar experiences, I'm sure this must have been a side effect of the propofol."