Will working up a sweat boost your immune system or make you sicker? Keep reading to learn when you should workout and when it might be best to rest, hydrate, and catch up on your Netflix queue. In general, our approach towards sickness has always been simple: if going to the gym can get others sick, then stay away. That counts for coughs, sniffles, sore throats, fevers, and anything that isn’t general fatigue. Remember, one day is just one day. That doesn’t mean you can’t workout at home when you’re sick, but try to think of others when you’ve got symptoms.