I am not sure if this would work, but I have read that it might be possible to make a kitten sneeze by stroking the back of his neck. This is usually done when they are about 2 weeks old and you can do it anytime after that. Also, some people try rubbing their hands on their wrists or even on the side of their head (somehow making them feel like there is something in those places). It may take several tries before your kitten will actually sneeze, but keep trying!! If nothing ever works at all, you probably should visit with your vet for an opinion what could be wrong with him. Good luck!