There are many places around the web where you mix peroxide and Dawn and use it as a stain remover. I got it from OneGoodThingByJillee.com, and she linked to a Glamour.com article about it. The basic recipe is that you use 1 part Dawn dishwashing liquid and 2 parts hydrogen peroxide to mix your own stain remover. However, Jillee also adds baking soda to it for scrubbing power.
I have been using this stain remover (with baking soda) for quite a while now. I have found that overall, it’s wonderful. For one thing, it not only takes out armpit stains, but it takes out even set in armpit stink. For several of my shirts, it took more than one application to get the stains out, but the stink was gone after the first wash (I’m sure the baking soda helped). It also takes out grease or oil stains (important when you’ve got a habit of spilling things on your clothes while cooking or eating).
The one drawback that I have found is that it sometimes bleaches colors a bit. This usually happens when you allow the remover to sit a while or when you have a newer piece of clothing that hasn’t been washed as much. If you can test an inconspicuous spot, I suggest you do so. Usually when I use it, it is with a piece that would otherwise be stuck in the “rags/paint clothes” pile, so I have nothing to lose. I just try to not let it sit more than five minutes before washing, and usually, it’s not a problem. However, before I knew it was a problem, I tried it on a new shirt for a grease stain. I really wish I hadn’t done that as it left a light bleach spot. I’ve been testing using just a mixture of Dawn and water with some baking soda for grease stains when grease is the only problem. So far, it seems to be working fairly well.
Here are pictures of pieces I’ve used the stain remover on: