soap will appear as an organic compound on the x-ray and depending on the circumstances might appear similar to some sort of explo. This shouldn't cause any issues when you explain what it is and they do the other checks (Barringer swab or similar), though some perfumes can give false positives with some testing equipment (not necessarily as explo though). I don't imagine it would cause any insurmountable problems, but one thing you could do is tweet [MENTION=334464]ASK[/MENTION]TSA as they're pretty good at responding with guidance or a yes/no, and that might also help if you did find a problem when travelling. Doesn't help at Dubai though to be fair!