ATS: Laundry Methods Matter for Busting Allergens

SAN FRANCISCO, May 20 -- Scalding hot wash water is most effective against allergens in the laundry, as allergists have recommended, but lower temperatures may be sufficient if an extra rinse cycle is added.

So found Jung-Won Park, M.D., Ph.D., of Yonsei University in Seoul, South Korea, and colleagues after washing hundreds of loads of laundry contaminated with dust mites, dog dander, and pollen.

"Rinsing after cleaning is especially important at low temperature cleaning for removal of allergens," Dr. Park said here at the American Thoracic Society meeting.

While laundering bedding and clothes has been known to be a key factor in controlling indoor allergens, the specifics have been less clear, he said.

So his group set up an experiment using a washing machine with four modes: a cold water wash (30?C or 86?F), a warm water wash (40?C or 104?F), a hot water wash (60?C or 140?F), and a steam-drum cycle.

Each load was washed with 35 g/70 L of enzyme-containing laundry detergent for a 40-minute wash cycle. Rinse cycles were run with cold water for 10 minutes each.

Contaminated laundry was simulated by putting house dust mites in mesh balls in two pillows and immersing cotton sheets in a solution with house dust mites, dog dander, and oak pollen.

The researchers measured remaining allergens with an ELISA assay and an ELISA inhibition test on pooled serum samples from atopic individuals.

For dust mites, they found:

• Cold water killed only 4.7% to 8.0%.
• Warm water killed only 7% to 10.7%.
• Both the hot water wash and the steam drum killed 100% every time.
• On the ELISA inhibition test, differences between cycles disappeared when rinsing two or more times.
• Results with the ELISA allergen assay were more variable, but were significantly worse with cold water than hot water or steam regardless of the number of rinses (P<0.05).

For the dog dander allergen Can f1, the findings were:

• Hot water and steam removed significantly more allergens than either cold or warm water when laundry was rinsed once or not at all (P<0.05).
• Nearly all allergens were removed by all wash temperatures when rinsing twice or more (0.0% to 0.01%, P=NS for all).

For oak pollen, the results were:

• Hot water was significantly more effective than cold or warm water when laundry was not rinsed (P<0.05).
• Rinsing at least once eliminated differences in pollen removal between wash temperatures.

The temperature findings confirm what allergists have been telling patients, said Asriani M. Chiu, M.D., of the Medical College of Wisconsin in Milwaukee.

"It's the higher temperature water that actually kills the dust mites and denatures the proteins," she said.

A limiting factor to this study, however, "is the actual application of it," said Neeti Gupta, M.D., of the Long Island Children's Hospital in Brooklyn, N.Y.

The hot water temperature used in the study was higher than the typical 120?F setting for hot water heaters here, Dr. Chiu noted. It is also higher than the 130? suggested by previous studies, Dr. Gupta said.

"What we end up telling families is you really need to turn up your water heater," Dr. Chiu said.

This can be a risk to young children, though, because the extra 10? or 20? "can be scalding," she said.

"We recommend that the family increase the temperature and do the laundry while the kids sleep or that they put a cover on the faucet," she added.

The finding that repeated rinsing of items washed at lower temperatures is effective may make life easier, she said.