actually mac has return policy where as long as you have the box it came in (if bought at mac's has to have that return label) or the receipt. as long as it is within 60-90 days im not sure which you can return or exchange it! That is all MAC policy. If you didnt have the box or receipt, of course you cant return it because of sanitary reasons. Sorry to hear about your reaction, MAC eyeshadows are highly pigment so if you are allergic to a type of coloring (for example red dye 40) or any other, even if you don't know about it, that could be what happened. but they always take it back as long as you have the receipt or/label for it. OR if you have already exchanged it a couple times, you will only be able to get an exchange.