Study: Bleach Cuts Allergy Triggers in Mold

Sept. 22, 2005 -- Diluted bleach can kill a common household mold and cut its allergy triggers, a new study shows.

"It has long been known that bleach can kill mold. However, dead mold may remain allergenic," says researcher John Martyny, PhD, in a news release.

"We found that, under laboratory conditions, treating mold with bleach lowered allergic reactions to the mold in allergic patients," he continues.

In the future, bleach should be scientifically tested against mold in real-world settings, notes Martyny. He is an associate professor of medicine at the National Jewish Medical and Research Center in Denver.

The study appears in The Journal of Allergy and Clinical Immunology and was partially funded by The Clorox Company, which makes bleach and other cleaning products.

Targeting Mold

The researchers focused on one type of household mold called Aspergillus fumigatus.

First, they grew the mold on squares of three building materials: plywood, gypsum drywall, and oriented strand board.

Next, the scientists sprayed the mold with distilled water, diluted bleach, or Tilex (a Clorox cleaning product that includes bleach as one of its ingredients).

Lastly, the researchers brought in 21 people who reported being allergic to mold. Eight of those people were shown to be allergic to the mold used in the experiment.

The mold died after being sprayed with diluted bleach or Tilex. Allergy triggers in the dead mold also faded in the bleach- or Tilex-treated building materials, the study shows.

Distilled water didn't kill the mold or tame its allergy triggers.

Allergic skin reactions were reduced with the bleach- or Tilex-treated molds. Since few allergic people were tested, a bigger study should be done, the researchers note.

Do-It-Yourself Fix?

The researchers' recipe for the diluted bleach was 1cup of household-strength bleach per gallon of water.

Some government agencies and mold contamination authorities do not recommend using household bleach to treat mold-contaminated buildings, partly because of concerns about allergies, write Martyny and colleagues.

They call for that advice to be reconsidered in light of their findings.

Other studies should check whether bleach kills different types of mold and mold on other surfaces, write the researchers.