The distinction between organic and inorganic carbon compounds, while useful in organizing the vast subject of chemistry... is somewhat arbitrary. Organic chemistry is the science concerned with all aspects of organic compounds. Organic synthesis is the methodology of their preparation.
No, it is not possible to contract the typical STDs, such as syphilis, gonorrhea, chlamydia, hepatitis B, etc. from wearing someone else's dirty underwear. However crabs and scabies, may be spread in this fashion.
Wearing underwear at night. According to reports, sleeping in the nude to air out the vagina is the way to go. Bedtime is, after all, the perfect time to let out all the sweat that has built up over the day. Scented body wash. Using scented body wash or even scented lotion near the vagina can cause odor. Laundry detergent. Scented laundry detergent or fabric softeners can irritate the vagina, once again causing odor. Wash your underwear separately with unscented detergent if this is the case.