Published by the Students of Johns Hopkins since 1896
April 17, 2026
April 17, 2026 | Published by the Students of Johns Hopkins since 1896

Ask a Scientist: How does bleach work?

By Husain Danish | February 25, 2009

It is Sunday evening, and I realize I have no more clean cloths; I need to do the laundry. I fill my basket with all my dirty clothes and detergents and haul it down to the laundry room.

I separate my colors from my whites and jam everything into the machine. When all is done, I add a touch of bleach. Then it strikes me: What is this stuff anyway?

"The definition of bleaching is to turn something white," Paul Dagdigian, a professor in the Chemistry Department, said. There are many different types of bleaches based on various chemical compounds. The most common are oxygen-based bleaches.

"Oxygen bleaches remove colors by oxidating the system," Dagdigian said. "Molecules in the bleach react with chemicals in a stain and break various chemical bonds. The result: What once had color is now colorless."

After I was done with my laundry, I went back to my room. To my great chagrin, the bathroom was dirty. I began to wipe the bathroom down with Clorox wipes, which also contain bleach. But why?

"Bleaches can also work as an antiseptic," Dagdigian said. "Bleaches oxidize organic materials like those that make up the cell walls of bacteria. The chemical reactions kill the bacteria."


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