Your shower drain can become very smelly due to the accumulation of bacteria inside the pipes. When it becomes wet, the odors are released into the air. In order to remove the odor, follow these tips.
Remove the Strainer
The strainer will either just pop out, or will be held in place with a couple of tiny screws. Remove it and soak it in vinegar to remove the slime and kill odor causing bacteria. You will then need to clean the pipe.
Next, you will need to take about half of a small box of baking soda and pour it down the drain. Follow this with half 2 cups of vinegar. Pour it all around the outside of the drain to try to get to the circumference of the drain pipe deep inside. You will hear a bubbling action occurring. That means it is working. Leave it for an hour. You'll then be ready to rinse and put the strainer back on.
Rinse and Reassemble
To rinse the smelly gunk on down the drain, pour a gallon of boiling water down the drain. The muck that was causing the odors will be gone. Reinstall your drain stainer and your done. In order to keep the smells away, pour one teaspoon of baking soda down the drain every day. Also wipe the strainer daily to remove hair and soap shavings.