It is one of those small household arguments that never really gets settled. One person in the house swears the curtain has to be pulled shut so the bathroom looks tidy. The other insists that closing it is exactly what grows the mildew nobody wants to scrub off. Search around and you will find confident, opposite advice depending on where you look, and neither side is entirely wrong.
Should you leave your shower curtain open or closed?
The short answer: Close the curtain fully, but stretch it out across the rod so it is not bunched into folds. That is the position Good Housekeeping Institute’s Home Care & Cleaning Lab currently recommends, since a curtain pulled taut lets enough air circulate around the top and sides to dry it out. Pair that with running the exhaust fan or cracking a window for 20 to 30 minutes after your shower. EPA recommends drying wet or damp materials within 24 to 48 hours specifically because prolonged moisture raises the odds of mold growth, so speed matters more than the exact position. If your bathroom has no working exhaust fan, leaving the curtain fully open instead gives it more direct airflow, which matters more there than tidiness does.
Moisture control is really the underlying issue, and it shows up in more places than the shower curtain. If your bathroom struggles with lingering humidity or mold in general, our guides to improving air quality in older homes and common bathroom problems in older homes cover the ventilation issues that make this worse.
Shower Curtain Open or Closed: At a Glance
Best overall practice
Closed, fully stretched across the rod, no folds
EPA and CDC ideal bathroom humidity
Below 60%, ideally 30% to 50%
EPA’s recommended window for drying wet materials
24 to 48 hours
Material most studied for shower curtain biofilm
Vinyl liners
Where microbes concentrate most
Folds along the bottom hem
Single most effective fix
Squeegee surfaces, then run the fan 20 to 30 minutes after
Key takeaways
Close the curtain, but stretch it out fully across the rod so it is not bunched into folds. Folds are a major place where moisture gets trapped, not the closed position itself.
EPA recommends drying wet or damp materials within 24 to 48 hours because prolonged moisture raises the odds of mold growth. EPA and CDC also recommend keeping indoor humidity below 60%, ideally between 30% and 50%.
A 2004 University of Colorado study found that vinyl shower curtain biofilms were dominated by Sphingomonas and Methylobacterium bacteria, concentrated in the folds, not mold in the technical sense.
Physically removing water with a squeegee or towel matters more than most people think, since it eliminates water that would otherwise have to evaporate.
If your exhaust fan vents into the attic instead of outside, running it after every shower can quietly create a mold problem up there instead of in the bathroom.
People with asthma, allergies, or who are very young or elderly face higher risk from mold g
