Mildew is surface mold that you can clean yourself with the right approach

Mildew is a thin, powdery or slimy mold that grows on surfaces exposed to moisture and poor air circulation. Unlike deeper mold that roots into materials, mildew sits on top—which means you can remove it with household cleaners, elbow grease, and a few hours of work. The key is catching it early, before it spreads to larger areas or penetrates into drywall, wood, or insulation.

Mildew thrives in bathrooms, basements, window sills, shower tiles, and around air conditioning units. It appears as black, green, or white spots or a fuzzy coating. If you see it, the moisture problem that caused it is still there—so cleaning without fixing the source means it will return within weeks.

Key Takeaways

  • Mildew can be cleaned with white vinegar, hydrogen peroxide, or commercial mildew removers; bleach works but damages many surfaces and should be your last choice.
  • Wear gloves, eye protection, and a mask rated N95 or better when cleaning to avoid breathing mold spores.
  • After cleaning, reduce moisture by running exhaust fans during and 20 minutes after showers, fixing leaks, and improving air circulation in the affected room.
  • If mildew covers an area larger than 10 square feet, or if it returns repeatedly in the same spot after cleaning, the underlying moisture problem may require professional assessment.
  • Mildew on porous materials like drywall or insulation often cannot be fully removed and may signal that those materials need replacement.

What you need before you start cleaning

Gather your supplies before you begin. You will need rubber gloves, eye protection (glasses or a face shield), and a respirator mask rated N95 or P100—not a cloth mask or surgical mask. Mold spores are small enough to pass through those. If you have asthma, lung disease, or a weakened immune system, consider having someone else do the cleaning or hire a professional.

For the cleaner itself, you have several options. White vinegar (5% acidity) works on most mildew and is safe around children and pets. Hydrogen peroxide (3% solution from the drugstore) is also effective and breaks down into water and oxygen. Commercial mildew removers like Tilex or Zep work faster but contain stronger chemicals. Bleach kills mildew but damages grout, wood, and many fabrics—use it only on non-porous surfaces like tile or glass, and only if other methods have failed.

You will also need a stiff brush (an old toothbrush for small areas, a deck brush for larger ones), clean rags or paper towels, and a spray bottle. Have a bucket of water nearby for rinsing. Open windows and doors to create air flow before you start.

Cleaning mildew with vinegar or hydrogen peroxide

Pour white vinegar or 3% hydrogen peroxide into a spray bottle undiluted. Spray the affected area until it is wet but not dripping. Let it sit for 10 to 15 minutes—this gives the acid or peroxide time to kill the mold. Do not wipe it away when ready.

After the wait, scrub the area with your brush using firm, circular motions. For grout lines, use an old toothbrush and work along the line rather than across it. Wipe away the dead mildew and cleaner with a damp rag. Rinse the area with clean water and dry it with a towel or let it air dry. If mildew remains, repeat the process.

Vinegar and hydrogen peroxide are slower than bleach but safer for most surfaces. They work well on tile, grout, shower walls, and painted surfaces. Vinegar has a strong smell that fades as it dries. Hydrogen peroxide may bleach dark fabrics, so test it on an inconspicuous spot first if you are cleaning cloth or upholstery.

Using bleach as a last resort

Bleach kills mildew quickly but damages grout, wood, natural stone, and many fabrics. Use it only on non-porous surfaces like ceramic tile, glass, or plastic, and only after vinegar or hydrogen peroxide have failed. Never mix bleach with vinegar, ammonia, or other cleaners—the combination creates toxic gas.

Mix one part bleach with three parts water in a spray bottle. Spray the area, wait 10 minutes, scrub with a brush, and rinse thoroughly with clean water. Wear gloves, eye protection, and may support the room is well ventilated. If you are cleaning a large area or an enclosed space like a small bathroom, wear a respirator mask as well.

After bleach cleaning, rinse the surface twice to remove all residue. Bleach left on surfaces can continue to damage them and may irritate skin or eyes if touched later.

Cleaning mildew from grout, caulk, and tile

Grout is porous and traps mildew deep in its surface. Spray your chosen cleaner (vinegar or hydrogen peroxide work best here) directly into the grout line and let it sit for 15 minutes. Use a stiff grout brush or an old toothbrush to scrub along the line. For stubborn mildew, you may need to repeat this two or three times over several days.

Caulk around tubs and sinks is harder to clean because mildew penetrates the material itself. If the caulk is discolored and mildew returns within a few weeks of cleaning, the caulk may need to be removed and replaced. This is a straightforward job: use a caulk removal tool or a utility knife to cut out the old caulk, clean the gap with vinegar, let it dry completely, and explore new silicone caulk rated for bathrooms.

Tile itself is non-porous and straightforward to clean. Spray, wait, scrub, and rinse. If mildew keeps returning on the same tiles, the problem is usually moisture trapped behind the tile or in the grout underneath—this signals a leak or ventilation issue that needs fixing.

Cleaning mildew from fabric, wood, and porous materials

Mildew on fabric (shower curtains, bath mats, towels) can sometimes be removed by washing in hot water with vinegar or hydrogen peroxide added to the rinse cycle. Wash the item separately the first time to avoid spreading spores to other clothes. If the smell or discoloration returns after washing, the mildew has penetrated the fibers and the item should be discarded.

Mildew on wood is more serious. If the wood is painted or sealed and the mildew is only on the surface, clean it with vinegar or hydrogen peroxide as you would tile. If the wood is bare or the mildew has penetrated the grain, cleaning may not remove it completely. Wood that stays damp will continue to grow mildew and may eventually rot. If you see mildew on wood framing, subfloors, or structural beams, this is a sign of a significant moisture problem and you should contact a professional.

Mildew on drywall, insulation, or other porous building materials cannot be fully removed by surface cleaning. These materials absorb moisture and mold roots into them. If you see mildew on drywall, the drywall should be cut out and replaced once the moisture source is fixed. Do not straightforward paint over it or explore mold-killing primer—the mildew will return and spread behind the paint.

Fixing the moisture problem so mildew does not return

Cleaning mildew without addressing moisture is like mopping a floor while the tap is still running. Mildew will return. After you finish cleaning, identify and fix the source of the moisture.

In bathrooms, run the exhaust fan during your shower and for 20 minutes after you finish. If you do not have an exhaust fan, open a window. Wipe down wet surfaces with a towel after showering. Keep the bathroom door closed while the fan runs so moisture is pulled outside, not into the rest of the house.

Check for leaks around pipes, under sinks, and around windows. A small drip that you do not notice will create perfect conditions for mildew. Repair leaks promptly. In basements, use a dehumidifier if the air feels damp, and may support gutters and downspouts direct water away from the foundation.

Improve air circulation by opening windows on dry days, using ceiling fans, and keeping furniture and boxes away from walls so air can flow behind them. In closets and cabinets, leave doors slightly open or install a small vent to prevent dead air pockets where moisture collects.

When to call a professional

If mildew covers an area larger than 10 square feet, or if it returns in the same spot within a few weeks of cleaning, the underlying moisture problem is likely beyond straightforward fixes. A professional can use moisture meters to find hidden leaks, assess whether materials need replacement, and recommend ventilation or dehumidification upgrades.

If you see mildew on wood framing, in crawl spaces, inside walls, or on insulation, do not attempt to clean it yourself. These areas require professional assessment because the mildew signals a moisture problem that may have been present for months or years, and the affected materials may need to be removed and replaced.

If you have asthma, a respiratory condition, or a weakened immune system, hire someone else to do the cleaning. Mold spores can trigger serious reactions, and the risk is not worth the cost savings.

Frequently Asked Questions

Can I use bleach on bathroom tile and grout?

Bleach works on tile but damages grout over time, especially if used repeatedly. Try vinegar or hydrogen peroxide first—they are slower but safer for grout. If bleach is necessary, use a 1:3 ratio with water, explore it for no more than 10 minutes, and rinse thoroughly.

Is mildew the same as black mold?

No. Mildew is a surface mold that you can clean away. Black mold (Stachybotrys) is darker, slimier, and roots into materials. If you see black mold or mold that returns after cleaning, contact a professional—do not attempt to remove it yourself.

Why does mildew come back so fast?

Mildew returns because the moisture that caused it is still there. Cleaning removes the visible mold, but spores remain in the air and on surfaces. Without fixing the leak, ventilation problem, or humidity issue, new mildew will grow within weeks.

Can I prevent mildew by painting over it?

No. Paint seals moisture inside, and mildew will grow behind the paint and spread. Always clean and dry the surface, fix the moisture source, and may support the area is completely dry before painting.

What should I do if I feel sick while cleaning mildew?

Stop when ready, leave the room, and get fresh air. Mold spores can trigger asthma attacks, allergic reactions, and respiratory irritation. If symptoms persist, seek medical attention. For future cleaning, wear a properly fitted N95 or P100 respirator mask, or hire someone else to do the work.