Flush the toilet several times and listen for a gurgling sound THIS means partial stoppage OR blocked vent.
If no sounds GREAT then continue with the following advice
What also causes this type of smell is TRAP SEAL LOSS which in most cases like a shower is caused by capillary attraction.
Try to picture an old cigarette lighter with a WICK that draws up the lighter fluid, the same with HAIR hanging over the crown weir (dip) of the trap.
The hair hanging over this trap is siphoning the water out and thus causing a trap seal loss and thus a smell of sewer gases.
Remedy have a plumber snake out the line and WATCH HIM and see how much hair is removed. Have the plumber snake this line SEVERAL times until the snake comes back clear ASK to see either a license or Journeyman’s card NEVER ever let an unlicensed tradesman in your home to dabble in this type of work.
Please keep me posted as I love hearing how the job turns out
[Edited by Moderator on 19 March 2001]