If you are simply moving the terrarium around or want to check the frog out, touching the frog generally won't hurt it. Keep in mind that it is easy to injure frogs, and care should be taken to avoid dropping them and such. Some species tolerate it better than others. I have had Agalychnis callidryas and A. annae that would grab crickets right out of my hands. One thing to avoid is touchimg frogs in one terrarium, and then going to another terrarium and servicing it. I would recommend nitrile gloves. Generally, i avoid touching frogs unless necessary.