TL;DR
Turn the shower cap inside out, hand wash it in warm water with a little dish soap or gentle detergent, rinse thoroughly, and hang it open to dry with air reaching both sides. Drying is the whole game: a shower cap that gets folded and stashed damp will smell musty within days, and once mildew has set into the lining it usually will not come out.
Why Shower Caps Go Musty
A shower cap has a waterproof outer layer, sometimes a fabric lining, and an elastic band. It spends its working life in the steamiest room in the house and then gets balled up.
Water gets trapped between the waterproof layer and the lining, and the elastic channel holds moisture longer than anything else. In a warm, dark, folded cap, that is ideal conditions for mildew. The smell arrives before the spots do.
The cap also collects whatever is on your hair and scalp: conditioner, oil, dry shampoo, and hair treatment. That residue feeds the problem and leaves a slick film on the inside. It is the same story as every other damp bathroom item in cleaning the personal items you use daily.
How Do You Clean a Shower Cap?
Turn the cap inside out and hand wash it in warm water with a few drops of dish soap or a gentle laundry detergent. Rub the lining and the elastic band gently with your fingers, rinse thoroughly until no suds remain, shake the water out, and hang it open so air reaches both surfaces. Let it dry fully before storing.
Turning it inside out is what makes the wash work. The dirty side is the inside, and washing the outside of a cap accomplishes almost nothing.
Handling a Musty Smell
If the cap already smells, a plain soap wash may not clear it. Soak the cap for thirty minutes in a basin of warm water with a half cup of white vinegar, then wash with soap, rinse thoroughly, and dry it completely in open air. Vinegar helps with mildew odor because it is acidic.
Sunlight and airflow help more than any additive. Hang the cap somewhere bright and breezy for a few hours after washing.
Never mix vinegar with bleach or any chlorine product, because that combination releases chlorine gas. And do not mix hydrogen peroxide and vinegar in one container, which produces corrosive peracetic acid. If you want to use an oxygen-based product, use it alone, following its label. Odor that returns after a thorough wash usually means mildew is established inside the layers, and at that point replacement is the honest answer, a decision explained more broadly in removing odors at the source.
Can You Machine Wash a Shower Cap?
Usually not a good idea. Machine agitation stretches the elastic band, can crack a waterproof coating, and may delaminate the lining from the outer layer. If you do machine wash one, use a mesh laundry bag on a gentle cold cycle and never put it in a dryer.
Heat is the bigger risk. A clothes dryer will shrink the elastic, melt some coatings, and warp the shape. Air drying is the only safe option regardless of how it was washed.
Drying: The Step That Decides Everything
Hang the cap open, brim down, over a hook, a towel bar, or the edge of a drying rack. The goal is airflow on the inside surface, which is the part that stays wet.
Do not fold it, do not stack it, and do not put it in a drawer or a travel pouch until it is completely dry, including the elastic channel. Squeeze the band between your fingers to check, because it holds water long after the rest feels dry.
Hang it outside the shower rather than inside it. A cap hung on the shower head or the inside of the door never gets a chance to dry, because the whole space stays humid. If your bathroom stays damp, run the exhaust fan for twenty minutes after every shower. That helps every item in the room, which is part of what routine work through bathroom cleaning by fixture is for.
How Often Should You Wash a Shower Cap?
Wash it every one to two weeks with regular use, and rinse and hang it after every use. Wash it sooner if you use hair oil, deep conditioner, or a hair treatment under it, since those leave a film that traps moisture and holds odor.
Treatment caps used for masks or oils need washing after every use. Product left inside the cap goes rancid faster than you would expect and is the usual cause of a cap that smells even when it looks clean.
Fabric-Lined and Decorative Caps
Caps with a fabric outer shell, a terry lining, or ruffles need more drying time, not different soap. The fabric holds water and the seams hold more.
Wash them the same way, then give them a full day to dry, ideally spread open rather than hung, so the seams get air. A fabric-lined cap that is used daily should be swapped with a second cap so each one has time to dry completely between uses.
Anything with glued embellishments should be spot cleaned rather than soaked, because adhesive lets go in warm water.
When to Replace It
Replace a shower cap when the elastic has stretched out and no longer holds, when the waterproof layer is cracked or peeling, when the lining has separated from the outer layer, or when spots or a smell persist after a thorough wash.
Visible black or dark speckling inside a cap is mildew growing in the material, and it does not scrub out of a laminated layer. Caps are inexpensive, so this is a straightforward replacement rather than a restoration project.
The same short service life applies to other porous bathroom items, which is why cleaning a loofah or bath pouf is mostly a replacement schedule, and why cleaning a rubber bath mat is really a drying routine. All three are downstream of how damp the bathroom stays and how often it gets attention, which is the case for putting the house on ongoing house cleaning rather than fighting each item separately.
FAQ
How do you wash a shower cap?
Turn it inside out and hand wash in warm water with a few drops of dish soap or gentle detergent, rubbing the lining and the elastic band. Rinse until no suds remain, shake the water out, and hang it open so air reaches both sides. Let it dry fully before storing.
Why does my shower cap smell musty?
Moisture is getting trapped between the layers and in the elastic channel, and the cap is being folded or stored before it dries. Hair product residue makes it worse. Wash it, soak it in a vinegar solution if the smell persists, and change how you dry it.
Can you put a shower cap in the washing machine?
It is best avoided. Agitation stretches the elastic, can crack the waterproof coating, and may separate the lining. If you do, use a mesh bag on a gentle cold cycle. Never put a shower cap in a clothes dryer, because heat shrinks the elastic and warps the shape.
Can you use vinegar to clean a shower cap?
Yes. Soak it about thirty minutes in warm water with a half cup of white vinegar to help with mildew odor, then wash with soap and rinse thoroughly. Never combine vinegar with bleach or any chlorine product, because that mix releases chlorine gas.
How do you dry a shower cap properly?
Hang it open, brim down, on a hook or towel bar outside the shower so air reaches the inside surface. Check that the elastic band is dry by squeezing it, since it holds water longest. Do not fold or store it until every part is dry.
How often should you wash a shower cap?
Every one to two weeks with regular use, and rinse and hang it after every shower. Wash it after each use if you wear it over hair oil, a deep conditioner, or a treatment mask, because that residue traps moisture and turns rancid.
When should you replace a shower cap?
Replace it when the elastic no longer grips, when the waterproof layer cracks or peels, when the lining separates, or when spots or a musty smell survive a full wash. Dark speckling inside the material is mildew, and it does not come out of a laminated layer.
Anything that lives wet in a bathroom needs a drying plan more than a cleaning plan. If you would rather hand off the wider routine, get a quote and we will walk you through it. Every home is different, so the real number depends on size, condition, and what you want covered.
