Yes, puking would not be proper in the dojo. If I have a headache then I agree with Mark, headaches are an alarm system telling you something is wrong. It is not something to play around with, there is a possibility of injury if it is tension, and dehydration could cause you to pass out. I say, personally if I have a headache, no matter what the cause, I am staying home because all that training and effort would be all for nothing if I had to restart after healing from an injury. One day off is better than a couple of months.