How to Get Rid of Black Mold in Shower Grout and Caulk

Quick answer: Here’s how to get rid of black mold in shower grout and tile: scrub it with a baking soda paste or an oxygen bleach solution and a stiff brush, let a diluted bleach or peroxide cleaner sit for 10 minutes on stubborn stains, then rinse and dry. Mold under silicone caulk can’t be cleaned out, so cut the caulk away and re-caulk. To keep it gone, squeegee after every shower and run the exhaust fan for about 20 minutes afterward.

If you’re wondering how to get rid of black mold in your shower, the good news is that it’s one of the most fixable mold problems in a house. Those black dots along grout lines and in the corners of the caulk are almost always surface growth living on soap scum and moisture.

Cleaning removes what you can see. The part most people skip is the habit change that stops it from growing back within a few weeks. This guide covers both.

What causes black mold in the shower?

Showers give mold everything it needs: water, warmth and food. Soap scum, body oils and skin cells build up in the rough surface of grout and along caulk lines, and the area stays wet for hours after every shower.

• Poor ventilation. No exhaust fan, a weak one, or a fan switched off right after the shower leaves humidity high for hours.
• Porous grout. Cement grout is full of tiny pores that hold water. Unsealed or worn grout stays damp the longest.
• Old or failing caulk. Once water gets behind or under silicone caulk, mold grows where you can’t reach it.
• Standing water. Bottles, loofahs and bath mats that trap water create permanent wet spots.
• High bathroom humidity. Windowless bathrooms and busy family bathrooms rarely dry out between showers.

Is black mold in the shower dangerous?

“Black mold” is a nickname, not a species. The dark spots in showers are usually common surface molds and mildew. Stachybotrys, the mold people often mean by “toxic black mold,” needs materials like drywall or wood that stay soaked for a long time, not glazed tile.

That said, any mold can trigger allergy or asthma symptoms in sensitive people, according to the CDC. If anyone in the home has symptoms, talk to a doctor, and let someone else do the scrubbing.

Is it mold or pink slime?

Pink or orange film around the drain and on the shower floor is usually a bacterium, not mold. It cleans up the same way, with scrubbing and a disinfecting cleaner, and it comes back for the same reason: moisture.

How to get rid of black mold in shower grout and caulk: step by step

1. Ventilate and gear up. Turn on the exhaust fan, open a window or door, and put on rubber gloves and eye protection. An N95 mask is a good idea if you’re sensitive to mold.
2. Clear the shower. Remove bottles, razors, caddies and the shower curtain liner. Toss old loofahs and sponges.
3. Remove soap scum first. Spray the walls and floor with a bathroom cleaner or dish soap solution and scrub. Mold sits in the scum, and cleaners can’t reach it through a greasy film.
4. Scrub the grout. Make a paste of baking soda and water, work it into the grout lines with a stiff grout brush, and scrub along the lines, not across them. For deeper staining, use an oxygen bleach (sodium percarbonate) solution mixed per the label and let it sit 10 to 15 minutes before scrubbing.
5. Treat stubborn stains. If dark spots remain on tile or grout, apply a diluted chlorine bleach solution (no more than 1 cup of bleach per gallon of water) or 3% hydrogen peroxide. Let it sit about 10 minutes, then scrub and rinse well. Don’t use bleach on natural stone.
6. Check the caulk. If black spots remain inside or under the caulk after cleaning, the mold is growing beneath the surface. Cleaning won’t fix it. Move to the next step.
7. Replace moldy caulk. Cut out the old caulk with a utility knife or caulk remover, scrape away every bit, clean the joint, and let it dry fully (at least 24 hours). Apply a 100% silicone caulk labeled mold- or mildew-resistant, and let it cure per the label before showering.
8. Rinse and dry everything. Rinse thoroughly with clean water, then dry the walls with a squeegee and towel. Leave the fan running.
9. Seal the grout. Once the grout is clean and fully dry (give it a day or two), apply a penetrating grout sealer. It won’t make grout mold-proof, but it helps it shed water.
10. Wash the extras. Machine-wash fabric or plastic curtain liners on warm with detergent, and scrub the door tracks and drain cover.

Never mix bleach with vinegar, ammonia, toilet bowl cleaners or other acids: it releases toxic gas. Use one product at a time and rinse between them. Wear gloves and eye protection, keep the room ventilated with the fan running and a door or window open, and keep kids and pets out until surfaces are rinsed and dry. Follow each product’s label, and don’t use bleach or acidic cleaners on marble or other natural stone.

Bleach vs vinegar: what actually works?

Bleach is great at removing the dark stain on hard, non-porous surfaces like glazed tile. It’s less effective on porous grout, because it mostly whitens the surface while moisture stays inside. The EPA notes that bleach isn’t usually needed for mold cleanup; removing the growth and fixing the moisture matters more.

Vinegar is a mild acid that can kill some surface molds and dissolve soap scum. It won’t remove deep stains, and it can etch natural stone and some grout over time. It’s fine for weekly maintenance, but it isn’t a miracle cure.

Oxygen bleach and hydrogen peroxide are good middle-ground options for grout: they lift stains, are gentler on colored grout, and don’t have chlorine bleach’s fumes.

How long does it take?

Cleaning a shower takes about an hour. Replacing caulk adds an hour of work plus drying and curing time, so plan to be without that shower for a day or two.

The equipment that helps

Most of the work is done with a brush, a squeegee and a cleaner you already have. What keeps mold from returning is getting the bathroom dry after each shower, and measuring humidity so you know when it isn’t.

If your bathroom stays above 60% humidity for hours after showers, a stronger exhaust fan does more than any gadget. For more ways to dry a small room, see our best small dehumidifier guide.

How to keep black mold from coming back

• Squeegee after every shower. It takes 30 seconds and removes most of the water mold needs. Wipe the corners and caulk line with a towel.
• Run the exhaust fan for about 20 minutes after showering. A timer switch makes this automatic. As a rule of thumb from the Home Ventilating Institute, a bathroom up to 100 sq ft needs about 1 CFM per square foot, with a 50 CFM minimum.
• Leave the door and curtain open. Spread the curtain so it dries flat, and leave the door ajar when nobody needs privacy.
• Store bottles off the floor. Use a hanging caddy so nothing sits in standing water.
• Clean weekly. A quick spray-and-rinse stops soap scum from building up into mold food.
• Keep bathroom humidity under 50%. The EPA recommends 30% to 50% indoors. Our guide on how to reduce humidity in your house has more ideas.
• Re-seal grout and replace caulk as needed. Seal grout about once a year, and replace caulk as soon as it peels, cracks or turns dark from underneath.

Spots on the ceiling above the shower come from the same steam. Our guide on how to get rid of mold on a bathroom ceiling covers painted surfaces, and how to get rid of mold on walls covers drywall outside the shower.

When to call a professional

Call a mold remediation pro or a tile contractor if tiles are loose or grout is crumbling (water may be getting behind the wall), if mold comes back within days of cleaning, if you see mold on the drywall outside the shower or on the other side of the wall, if the affected area is larger than about 10 square feet (the EPA’s guideline), if there’s a musty smell you can’t trace, or if anyone in the home has health symptoms. A slow leak behind a shower valve is a common hidden cause.

Frequently asked questions

What kills black mold in a shower permanently?

No cleaner kills it permanently, because new spores land every day. What works long term is removing the growth, replacing moldy caulk, sealing grout, and keeping the shower dry with a squeegee and exhaust fan. Mold needs moisture to grow, so a shower that dries out within an hour of use rarely gets it back.

Can I use bleach on shower grout?

Yes, carefully. A solution of no more than 1 cup of bleach per gallon of water lifts dark stains from grout and tile. Ventilate, wear gloves, rinse well afterward and never mix it with vinegar or ammonia. Oxygen bleach is a gentler choice for colored grout. Avoid bleach on natural stone.

Why does black mold keep coming back in my shower caulk?

Because it’s growing under the caulk, where cleaners can’t reach. Water seeps behind caulk that has pulled away or aged, and mold grows in that dark, damp gap. The only fix is to cut out all the old caulk, clean and dry the joint for at least 24 hours, and apply fresh mold-resistant silicone.

Is vinegar or bleach better for shower mold?

Bleach is better at removing dark stains on non-porous tile. Vinegar is better for dissolving soap scum and for gentle weekly cleaning. Neither fixes moisture, which is the real cause. Use one or the other, never both together, and don’t use either on natural stone like marble or travertine.

How often should I clean my shower to prevent mold?

A quick spray-and-rinse once a week, with a squeegee after every shower, keeps most showers mold-free. Do a deeper grout scrub every month or two, seal grout about once a year and inspect caulk a few times a year for peeling or dark spots underneath.

Is it safe to shower with black mold?

For most healthy people, small spots of surface mold in a shower aren’t an emergency, but it’s worth cleaning soon. People with allergies, asthma or weakened immune systems can be more sensitive to mold, according to the CDC. If you notice symptoms, clean the mold, improve ventilation and talk to your doctor.

For mold elsewhere in the house, from basements to window sills, start with our complete guide on how to get rid of mold.