Think I have a nasal passage issue and more. Smells like vinegar or more likely, propionic acid. Maybe systemic? ...four weeks now for obvious nasal passage acid. Skin oils around nose and chin also have same odor. Stool has has unusual scent since a trip to Lima, Peru 5 months ago. Searching the net. Literature suggests might be propionic acid producing bug. Others on blogs have experienced similar symptoms as well. Lots of questions, no answers. Talked to a doc friend, puzzled, no answers. I m a 76 yr., male, slim, some weight loss in 5 months. Have always been unusually healthy. I m a biochemist, not a physician and certainly not a diagnostician...