Why Does My Washing Machine Smell Like Mildew And How To Deep Clean It Safely

If you've opened your washing machine lately and been greeted by a musty, damp odor reminiscent of old gym socks or a basement after rain, you're not alone. Mildew smells in washing machines are surprisingly common—even in machines used regularly. The irony is that a device meant to clean clothes can itself become a breeding ground for bacteria, mold, and unpleasant odors. This issue affects both front-loading and top-loading models, though front-loaders are more prone due to their design. Understanding the root causes and knowing how to deep clean your washer properly can restore freshness and protect your laundry—and your health.

Why Your Washing Machine Develops a Mildew Smell

The primary reason washing machines develop a mildew-like odor lies in moisture retention combined with organic buildup. Unlike dryers, which use heat and airflow, washing machines cycle water, detergent, and fabric softener—often leaving behind residues that cling to seals, gaskets, drums, and internal hoses. When these moist environments remain undisturbed, they create ideal conditions for microbial growth.

Front-loading machines are especially vulnerable because of their rubber door gasket. This seal keeps water from leaking during cycles but also traps water, lint, hair, and soap scum. Over time, this trapped debris decomposes slightly, feeding mold and mildew colonies. Additionally, many modern detergents are low-sudsing (designed for high-efficiency machines), which means they don’t rinse away as effectively, leaving behind film that microbes thrive on.

Other contributing factors include:

• Infrequent cleaning: Most people never think to clean their washing machine until the smell becomes unbearable.
• Leaving the door closed: After use, keeping the lid or door shut prevents ventilation, trapping humidity inside.
• Using too much detergent or fabric softener: Excess suds leave residue that builds up over time.
• Cold water washes: While energy-efficient, cold cycles don’t kill bacteria or dissolve grease and oils as effectively as hot water.
• Drain pump filter blockages: A clogged filter restricts drainage, allowing stagnant water to sit in the system.

“Moisture and organic residue are the perfect storm for microbial growth in appliances. Regular maintenance isn’t optional—it’s essential.” — Dr. Lena Torres, Environmental Microbiologist at CleanAir Labs

Tip: Always leave the washing machine door and detergent drawer open after each use to promote drying and reduce moisture buildup.

Step-by-Step Guide to Deep Cleaning Your Washing Machine

A thorough deep clean should be performed every 1–3 months, depending on usage. Follow this detailed process to eliminate odor-causing buildup safely and effectively.

1. Clear the area: Remove any clothes, dryer sheets, or forgotten items. Check pockets one last time if recently used.
2. Inspect and clean the rubber gasket (front-loaders): Pull back the rubber seal around the door and wipe down all visible surfaces with a microfiber cloth soaked in equal parts white vinegar and warm water. Pay special attention to crevices where black slime may accumulate.
3. Remove and clean the detergent drawer: Slide out the tray (usually removable with a gentle pull). Soak it in warm, soapy water. Use an old toothbrush to scrub compartments, then rinse thoroughly before reinserting.
4. Clean the drain pump filter (if accessible): Consult your user manual for location. Place a towel underneath, open the filter cover slowly, and remove any lint, coins, or debris. Rinse the filter under running water.
5. Run a hot cleaning cycle: Set your machine to the hottest, longest cycle (typically “Clean Washer,” “Tub Clean,” or “Sanitize”). Add one of the following:
   • 2 cups of distilled white vinegar
   • OR ½ cup of oxygen-based bleach (like OxiClean) — avoid chlorine bleach unless specified by manufacturer
6. Pause mid-cycle: After the tub fills, pause the cycle and let the solution soak for 30–60 minutes. This allows the cleaner to break down biofilm and loosen grime.
7. Resume and complete the cycle: Let the machine finish the full wash and drain sequence.
8. Wipe down interior surfaces: After the cycle ends, use a vinegar-dampened cloth to wipe the drum, door, and edges. Dry with a clean towel.
9. Deodorize with baking soda (optional): Run a second short cycle with ½ cup of baking soda added directly to the drum for extra freshness.

Tip: Never mix vinegar and chlorine bleach—they produce toxic chlorine gas. Stick to one cleaning agent per session.

Do’s and Don’ts of Washing Machine Maintenance

Do’s	Don’ts
Leave the door and detergent drawer open between uses	Close the door tightly immediately after washing
Use high-efficiency (HE) detergent in correct amounts	Overuse detergent or fabric softener
Clean the gasket and dispenser monthly	Ignore visible mold or slimy residue
Run a cleaning cycle every 4–6 weeks	Use harsh abrasives or steel wool on the drum
Check pockets and remove tissues before washing	Wash excessively dirty loads without pre-treating

Real Example: How Sarah Fixed Her Persistent Odor Problem

Sarah, a mother of three in Portland, Oregon, noticed her towels were coming out smelling worse than when they went in. Despite using premium detergent and running regular cycles, a persistent mildew stench lingered. She initially blamed her well water, but after consulting a technician, she learned the real culprit: years of neglecting the rubber seal and overusing fabric softener.

She followed a deep-cleaning protocol similar to the one above. After removing a thick layer of black gunk from beneath the gasket and running two consecutive vinegar cycles, the smell vanished. More importantly, she changed her habits—switching to liquid HE detergent, reducing softener use, and leaving the door ajar. Six months later, her machine remains odor-free and her laundry consistently fresh.

This case illustrates that while deep cleaning helps, long-term results depend on consistent preventive practices.

Best Products for Safe and Effective Cleaning

While DIY solutions like vinegar and baking soda are effective and affordable, commercial washing machine cleaners offer convenience and targeted formulations. Here's a comparison of popular options:

• Affresh Washer Cleaner: Designed for Whirlpool, Maytag, and Amana brands. Tablet form dissolves easily and targets lime and soap scum.
• Smelly Washer No More: A natural enzyme-based formula that breaks down organic buildup without harsh chemicals.
• Glisten Washer Magic: Removes hard water deposits and odors; safe for most machine types.
• DIY Vinegar & Baking Soda: Inexpensive and eco-friendly. Use separately—not mixed in the same cycle.

Regardless of product choice, always check your manufacturer’s guidelines. Some brands, like Samsung and LG, explicitly recommend against vinegar due to potential damage to rubber seals or sensors over time.

“Enzyme-based cleaners are gaining popularity because they digest organic matter instead of just masking odors. They’re especially useful for households with sensitivities to strong chemical fumes.” — James Reed, Appliance Technician and Home Efficiency Consultant

Preventive Checklist: Keep Your Machine Fresh Month After Month

To avoid recurring odors, adopt these simple yet effective habits:

• ✅ Leave the door and detergent drawer open after every wash
• ✅ Wipe the rubber gasket weekly with a dry or vinegar-dampened cloth
• ✅ Use only HE-rated detergent in recommended amounts
• ✅ Avoid overloading the machine—this reduces rinsing efficiency
• ✅ Wash workout clothes and towels in hot water when possible
• ✅ Run a cleaning cycle with vinegar or approved cleaner every 4–6 weeks
• ✅ Remove wet clothes within 30 minutes of cycle completion
• ✅ Inspect and clean the drain filter every 2–3 months

Tip: Place a moisture-absorbing pack (like silica gel or a reusable dehumidifier bag) inside the drum when not in use to reduce ambient humidity.

Frequently Asked Questions

Can I use bleach to clean my washing machine?

Yes, but with caution. Chlorine bleach can sanitize and remove mold, but it may degrade rubber components over time. Use only if your manufacturer approves it, and never mix it with vinegar or ammonia. For routine cleaning, oxygen bleach (sodium percarbonate) is safer and equally effective.

Why does my top-loader smell if it doesn’t have a rubber seal?

Even top-loading machines can harbor mildew. Residue builds up along the drum walls, beneath agitators, and in the outer tub that’s not visible. Detergent and fabric softener sludge can settle in crevices and breed odor-causing bacteria. Running periodic hot cleaning cycles with vinegar or a dedicated cleaner resolves this.

Is it safe to wash baby clothes in a machine that had mildew?

Once thoroughly cleaned and sanitized, yes. However, ensure you run at least one full cleaning cycle followed by a rinse-only cycle to remove any residual cleaner. For sensitive skin, consider washing infant garments in hot water with an extra rinse until you’re confident the machine is fully restored.

Conclusion: Take Control of Your Machine’s Hygiene

A smelly washing machine isn’t just unpleasant—it’s a sign of hidden contamination that can transfer to your clothes, irritate skin, and shorten the lifespan of your appliance. The good news is that with a little knowledge and consistent care, you can eliminate mildew odors and keep your washer running efficiently for years. The process doesn’t require expensive tools or professional help. What it does require is awareness and action.

Start today: inspect the gasket, run a cleaning cycle, and commit to simple daily habits like leaving the door open. Small steps lead to big improvements in hygiene, performance, and peace of mind. Your clothes—and your nose—will thank you.

💬 Have you successfully eliminated a stubborn washing machine odor? Share your method or questions in the comments below—your experience could help others break free from the mildew cycle!