* As a brand name: If you're referring to a specific brand of bleach, like Clorox, then you should capitalize it.
* As a general term: If you're talking about bleach in general, like "I need to bleach my clothes," then you wouldn't capitalize it.
Here are some examples:
* Capitalized: "I bought a bottle of Clorox bleach."
* Not capitalized: "I used bleach to get the stain out."