Never tune your guitar strings up. Guitar necks are set up to withstand a certain amount of tension. When the strings are tuned up, the added tension may warp the neck if left in that tuning, making the guitar difficult to play.
Some alternate tunings require one or more strings to be tuned up slightly. This is ok if done on a limited basis, however, you should always tune your guitar back down when you’re finished playing. If you plan on using an alternate tuning on a regular basis, you may want to check with an expert about setting up the guitar to handle the tension.
If you’re wondering, tuning your string down is perfectly safe and is far more common than tuning up.
