Where I can sympathise with his sinus problems, he is obviously having a tough time with them, he needs to be more considerate and go to the Men's toilets and get rid of it all, it is offensive to other people, and not at all pleasant to hear for sure, what country does he come from? maybe you are right, it is ok in his country to do this, I think a hint like some have suggested is your best bet, if that does not work then I am afraid you might have to use the direct approach, good luck.