Most people think that when they are sick that it is okay for them to work out to sweat out the sickness and the toxins. While it may be good to sweat, it is not good to exercise and try to be active. People that are sick should be advised to stay in bed. When someone gets sick, their body is internally fighting bacteria.
This is a way for their body to tell them that they need to take a break and get some rest. One day without exercise will do no harm. It is actually good to take days of rest sometimes so that the body has time to recooperate itself.
No I advise that you shouldn't work out. Feeling "sick" is your body's way of telling you to rest since it is internally fighting bacteria in your body. Sitting out a day or two don't do you much damage, just make your diet is in check when you're missing time from the gym.