from what i hear,that frolicle test can detect back trace's as far as 3month's,so if that's the case you should be o'kay,but if you don't want to take any chance's you might want to try a method (that i've never used myself)that's supposed to work,wash you're scalp with clarifying shampoo,work up a good lather,and use a medium heat hair dryer on your lathered hair for about 15 minute's,then rinse out,do this a least 3 hour's or less before the test....good luck....bonbon