If you have been in your current home for more than five years, make sure you inspect your caulking in your shower or your tub surround. Look for an appearance where the edges of the caulk are either peeling or have a break in the body of your caulk. If either of these are the case at your home, you need to either call a professional for or try to repair this situation yourself.
Remember, to have an effective outcome with this repair you MUST use SILICONE caulk. DO NOT USE latex or latex-siliconized caulk-they only last for six to twelve months.