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Can Clothes Look Clean, But Smell Stinky?

Scientists crack the case


For thousands of years, we’ve faced the challenge of cleaning clothes—and it remains a basic human need. In the past, this need was mainly driven by a simple fact: clean clothes last longer. The sweat, salt, natural oils and dead  skin  cells our bodies shed every day bind to and progressively damage textile fibers, and effective cleaning helps slow this process of deterioration.


But today’s laundry challenges go beyond simply making clothes last longer. In fact, promising new research by P&G Tide and Downy scientists has brought to light an association between mood, behavior, and the cleanliness of the clothes we wear. Intuitively, this makes sense, since no one wants to show up to a date or a job interview with clothes that are stained—or worse, stinky. However, there is now available hard scientific data to back up what we’ve long assumed.


There are new cleaning challenges stemming from trends in the textile industry. Due in large part to the trend in wearing athleisure clothing more frequently, synthetic fibers like polyester and elastane have become so popular that they now account for 64% of global fiber consumption. But here’s the rub: these fibers attract more greasy body soils and are therefore harder to clean. In fact, regular clothing made from synthetics and synthetic blends, not just  athletic gear, often suffers from “permastink” or “odor rebloom” (when clothes smell fresh out of the wash but begin to smell soon after we put them on)—even repeated washing results in an unpleasant smelling garment.



This is especially frustrating for the nearly 50% of people who say clothes can look clean after a wash, but still smell bad. To delve deeper into this, Tide scientists created a new method that relies on complex analytical equipment for highly sensitive findings, but also takes into account how most people detect odors on clothes—by sniffing them!


To measure odor reduction on clothing, Tide scientists used artificial body soils (ABS) dissolved in a solution which they then applied to swatches of fabric via pipette. They used the swatches to identify two primary means of eliminating odor: cleaning the fabric to remove the ABS odor  compounds from the fibers of the fabric, and second, how perfume or other ingredients prevent or limit a person’s ability to perceive odor by masking it with scent.


Fifteen different commercial laundry detergents were blind-tested by washing ABS-treated fabric swatches then assessing for odor by analytical and sensory measurements one day later. In the analytical assessment, a third of the 15 detergents studied did not clean the ABS odor compounds from fabric swatches any better than water alone. Such an analytics were based on the measurement by gas chromatography and mass spectroscopy for the presence of odor molecules in the “head space” of the fabrics. But that’s not all. When sensory panelists performed a sniff test a day after washing, they were unable to detect substantial odor differences between some detergents that removed ABS  well from those that did so poorly. These findings suggest that perfumes in some detergents may temporarily mask  the smell of odors that were not removed from the fabric swatches, which were washed in detergents that ranked at the bottom of the analytical assessment.


This research may also solve another laundry mystery: why seemingly clean, fresh-smelling clothes appear to pick up odors or begin to smell shortly after customers put them on. With 70% of laundry soils produced by our own  bodies remaining largely invisible to the human eye, poor-performing detergents continue to fail to remove such invisible body soils, leaving the remaining soils to break down over time. These remaining soils then release potent odor molecules that can leave clothes smelling stinky even after they are washed. This becomes most noticeable after the detergent’s perfume fades and the masking effect is gone.


Since customers want to look, feel (and smell) their best—washing their clothes with a high-quality detergent may not only offer advantages to their mood and confidence, but to your company’s overall financial confidence as well.


By Mary Begovic Johnson, Tide® and Downy® Principal Scientist