No ammonia, peroxide or bleach. It's supposed to shrink the color molecules that attach to your hair so that they wash right out.
Extra Strength Hair Color Remover | Color Oops | Beauty & Spa | Walgreens
a review from the link above:
It doesn't get any easier than mixing the contents of bottle 1 into bottle 2. You don't even have to shake it. Just 'tip it over' a few times.
My boyfriend went into the bathroom after I used color oops and he said it smelled like "bad eggs," or, something comparably putrid.
A few weeks ago I colored my hair ashy blonde. But because my ends were so light from being highlighted (and from sun exposure), they really absorbed the dye and just became a tint of dark grayish-green. The rest of my hair took the color well, but when I then tried to highlight on top of that, the highlights turned a white-ish yellow!
I just wanted to start over!
Color oops will take the dye out. However- and this is on the box- it WON'T take you to your original color if you have EVER lightened your hair.
If your hair is in good condition then this product won't do any harm.
The box also says that you can re-color the same day but I advise against this. All hair color kits recommend that you wash your hair no sooner than the day before you are going to color your hair and especially after removing color you'll want to let your hair's natural oils build up to protect it a little.