My son used to have a problem with sweating and staining his shirts. I think it outgrew it but he thinks it is more that we switched from regular antiperspirant to a natural antiperspirant. Anyway, he always stained his shirts. This will get out anything. Almost anything at least. I had the carpet cleaners tell me I would never remove a carpet stain and I got it out with this. This works on collar stains too. You use regular Dawn - blue. Pout the Dawn on the stain. Sprinkle a little baking soda on it too. Pour a teaspoon or two of peroxide on the stain. I scrub lightly with an old toothbrush. Let sit at least an hour or two then wash as usual. It is a set in stain, you may have to do this twice but it will be gone. I have yet to find anything that peroxide ruined. It simply doesn't harm anything. Try it, you will be pleasantly amazed.