VR is generally safe to use, BUT different people tolerate it in different ways. Nausea and headache are NOT uncommon among CR users, and things can be done to minimize the discomfort. Such as using VR with in limited doses, say 10 minutes at a time. Making sure you are in a comfortable cool environment, and you are seated or have you feet firmly planted on solid ground. NOT all VR is created equal! Some VR games and experiences are more intense than others and this is usually noted somewhere before it starts or on it's download page, etc. Avoid the ones that are too intense.
VRHeads has a sub forum dedicated to Health and Safety it can be found
here