You know, I sort of noticed this as well whenever I visited the engineering building in my university, this being the usual stomping grounds for most overseas foreigners. Granted that I wasn't all that well versed in differentiating between people of Arab or Indian descent, but they certainly did emanate a distinct odor. It certainly wasn't anything foul or anything of the sort, in fact it almost smelt somewhat appetizing, like an exotic Mexican spice, or comino or something.