The average water temperature recorded across real household laundry cycles was just 13.98°C (Frontiers in Microbiology, October 2025). At that temperature, microbes aren't being killed; they're getting redistributed across wet fabric. The musty, "wet-and-dustcloth-like" smell associated with laundered textiles has been specifically linked to bacterial colonizers of washing machines and low-temperature wash cycles (Microorganisms, 2022).

The machine itself compounds the problem. A Frontiers in Microbiology study, based on swabs from 10 household machines recruited through convenience sampling in New York and New Jersey, found that front-load washers harbored average bacterial counts of 6.50 ± 2.46 log₁₀/swab, compared to 3.79 ± 1.73 log₁₀/swab in top-loaders (Frontiers in Microbiology, October 2025). A contaminated machine reintroduces microbes during the wash cycle, which helps explain why odor returns quickly even after laundering.

When the smell appears points to different causes:

• Smell immediately after the wash cycle ends: likely a machine contamination or cold-wash issue; bacterial load wasn't meaningfully reduced during the cycle.
• Smell develops after the towel air-dries or is used once: likely post-wash regrowth. Bacterial counts on towels climbed back to near-prewash levels within 24 hours of humid indoor drying, even in towels washed with antibacterial detergent, under controlled conditions simulating high-humidity indoor air-drying (iMeta, 2023).
• Smell is mild but never fully goes away: often both problems together, compounded by infrequent washing or towels that never fully dry between uses.

Bacteria also have a ready food supply: residual soap, shed skin cells, and sustained moisture. The longer between washes and the less thoroughly towels dry, the larger the microbial population they sustain, according to Charles Gerba, an environmental science professor at the University of Arizona whose research is cited by Consumer Reports (updated July 2026).

Before starting: Check care labels. Most standard cotton bath towels tolerate hot water (up to 60°C / 140°F) and high-heat machine drying. Blended or decorative towels often don't. Do not use bleach on colored towels.

Step 1: Clean the washing machine

Run a hot, empty cleaning cycle using a washing machine cleaner tablet or powder. If the machine manual permits it, a small amount of chlorine bleach in the drum works as an alternative. For front-load machines: wipe down the rubber door gasket with a damp cloth after the cycle, clear debris from the drain filter, and leave the door propped open until the interior is completely dry.

Check: No residual odor from inside the drum. If it still smells musty, run a second cleaning cycle before putting towels in.

The Frontiers study concluded that common household laundry practices may not be sufficient to eliminate microbial contamination from machines, and called for additional sanitization strategies, particularly relevant for front-load owners (Frontiers in Microbiology, October 2025). Rewashing towels in a contaminated machine produces results that last about as long as the drum stays wet.

Vinegar warning: Don't add white vinegar to the machine dispenser unless the owner's manual explicitly permits it. Vinegar can damage rubber seals and hoses, potentially causing leaks, which creates a far worse mold problem than a smelly towel, per Consumer Reports (September 2025). If vinegar is used at all, apply it cautiously to individual garments rather than running it through the machine.

Step 2: Rewash towels in hot water with an effective detergent

Wash towels separately on the hottest cycle the care label allows. For persistent odor, an antibacterial detergent offers a measurable advantage: one controlled study found it reduced towel bacterial load by 1.45 log₁₀, a statistically significant reduction (p = 1.5 × 10⁻⁷), and specifically decreased the abundance of malodor-producing species while lowering emissions of dimethyl disulfide, a key odorant compound (iMeta, 2023). That study used hand-towel swatches washed at 25°C under controlled conditions, so real-world results may vary, but the directional finding is clear.

For odor that doesn't respond to a hot rewash, escalate in this order:

• Add a laundry sanitizer (e.g., Lysol Laundry Sanitizer or a Clorox equivalent) to the cycle. Gerba notes that thick towel fibers can insulate bacteria from hot water alone, making a sanitizer a useful addition (Consumer Reports, updated July 2026).
• For white cotton towels only: soak in a diluted bleach solution before rewashing. This is a last resort, per CR laundry expert Rich Handel (Consumer Reports, September 2025).
• If the machine has a sanitize cycle and the towels are strong cotton, use it. The minimum temperature generally cited for effective disinfection is 140°F, and sanitize cycles are designed to reach it (Consumer Reports, updated July 2026).

Don't put smelly towels in the dryer before rewashing. Handel notes the dryer can lock in existing odors rather than drive them out (Consumer Reports, September 2025).

Step 3: Dry towels promptly and completely

Transfer towels to the dryer immediately when the wash cycle ends. Wet laundry left sitting in the drum can develop mold within 24 to 48 hours (Consumer Reports, September 2025). Use a normal or heavy-duty cycle; residential dryers typically run between 120°F and 160°F (Consumer Reports, updated July 2026).

One study found that machine drying did not significantly decrease microbial loads on its own (Frontiers in Microbiology, October 2025). That doesn't mean drying doesn't matter; it means drying isn't a disinfection step. What it does is remove the moisture bacteria need to regrow. A completely dry towel stays odor-free. A damp one won't.

• Don't overload the dryer. A dense load traps moisture in the center. If towels feel even slightly damp when removed, run a second shorter cycle.
• Skip dryer sheets. They can leave a film on the moisture sensor, causing the dryer to misread dryness and over-run, and they reduce towel absorbency over time. Wool dryer balls soften towels without those side effects (Consumer Reports, updated July 2026).

On indoor air-drying: The research is unambiguous. Even after washing, bacterial counts rebound within 24 hours under humid indoor drying conditions (iMeta, 2023). Machine drying is more effective for odor control. If air-drying is the only option, maximize airflow and minimize humidity.

Step 4: Change the habits that restart the problem

Bath towels: The American Cleaning Institute recommends washing every three to five uses, with the towel hung fully spread to dry between each use (Consumer Reports, updated July 2026). Shower twice a day? Alternate between two towels so each one dries out completely before its next use.

Hand towels: Gerba recommends washing hand towels every three to four days. They're used more frequently than bath towels, often by multiple people, and they rarely dry out fully between uses. Gerba's own research found that the longer between washes, the more bacteria in the towel, as reported by Consumer Reports (updated July 2026).

Additional habits worth keeping:

• Hang towels fully spread after every use. Not folded over a bar, not dropped on the floor.
• Wash towels with towels only. Lint transfers to other garments, and mixing load types can mean uneven drying for thick fabrics.
• Front-load washer owners: leave the door open after every cycle. A sealed door holds moisture, which feeds the same bacterial ecosystem that ends up in the next load.

When to give up on a towel: If the smell persists after machine cleaning, a hot rewash with sanitizer, and full machine drying, the towel may have permanent fiber damage, deep residue buildup, or microbial colonization that routine washing won't reverse. Replacement is the practical call.

• Scent beads: Layer fragrance over bacteria rather than eliminating them. CR's experts are direct: scent beads cover the smell, they don't remove its cause (Consumer Reports, updated July 2026).
• Fabric softeners: Coat towel fibers with a residue that reduces absorbency. CR's testing team calls them a waste of money for towels (Consumer Reports, updated July 2026).
• Baking soda: May help soften water in hard-water areas, but CR's laundry expert notes that odor benefits haven't been independently tested (Consumer Reports, January 2024). Not a substitute for higher wash temperatures or machine cleaning.
• Cold rewash without machine cleaning: Running another cold cycle through a contaminated machine doesn't address either root cause. It's the equivalent of rinsing a glass in dirty water.

The right fix depends on when the odor shows up:

Antibacterial detergent produces a statistically significant reduction in odor-causing bacteria and the volatile compounds they generate, useful for persistent cases, though one controlled study isn't a universal prescription (iMeta, 2023). Front-load washer owners face a higher baseline bacterial load in their machines and should treat regular cleaning as essential, not optional (Frontiers in Microbiology, October 2025). Washing every three to five uses with proper drying in between remains the most practical prevention, simpler and more reliable than any additive (Consumer Reports, updated July 2026).

If the smell survives the full process, the towel is the problem. Not the process.