Virtual reality has returned. After more than a decade out of the spotlight, Facebook placed a big bet on the technology earlier this year by purchasing the pioneering company Oculus VR in a $2 billion dollar deal. VR has taken center stage at a wide variety of events as marketers have turned out incredibly immersive experiences for consumers to experience.

Under all of this new buzz is an unfortunate fact about VR. When using the head-mounted displays, some people experience a kind of motion sickness, known as “sim sickness”. The most common symptom is nausea. But when it comes to the ailment, the medium-term effects are much more complex, according to researcher Dr. Kay Stanney.

One problem is the resulting temporary instability and challenges to hand-eye coordination. “We equated the after effects [of VR] to blood alcohol level,” Stanney says. “[Users will] be done gaming and they’ll be drunk, physiologically.” The resulting “sim sickness” could last as long as an hour or more after a VR experience.

The heart of the problem is that VR creates a disconnect between what the eye sees and the body feels. Motion sickness, and why some are affected more than others, is not fully understood. In this way, VR is similar to riding in a car. Passengers are more likely to experience motion sickness than drivers, because drivers can anticipate where the car will be going.

Research has used this to design improved software that controls the conflict between the eye and the gut. Time is another factor on the side of virtual reality hardware makers. With enough exposure, the body itself appears to be capable of jumping between reality and the altered state of VR

Many engineers think there is a way to design VR games with an eye towards stopping the worst effects. It is believed that once VR becomes more mainstream, sim sickness will be avoided by the maturity of both the hardware and software.

While virtual reality has been worked and researched for decades, it is still a new technology. And every problem that stops a safe and enjoyable experience puts consumer VR at risk. All of this indicates that continued improvements are in the best interests of hardware makers.