Yeah, secreting toxins is possible. Just like with those oriental foot pads I've been seeing on TV recently. Don't know what they are called...
It doesn't make any sense that it would stain her hands though. Sweating it out, sure, but staining the skin? I don't see how that's possible. The toxins leave the body, that's been medically proven. They don't stay in the skin.
That photo looks photoshopped to me anyway.
OK but that photo is actually offered BY the Scientologists as proof that something good is happening, so they would be faking their own evidence if that is true - the picture is directly from the website of the program that Tom Cruise started for the 9/11 firefighters.