Brief holding is fine. I often feed my female Gray Treefrog while she sits on my hand. Some frog species are more sensitive than others but treefrogs are among the tougher of the bunch. I usually wash my hands with "normal" soap, then rinse and dry well with a towel, before holding frogs. I then wash my hands well afterwards. There are caresheets and info sheets (even by experts) who say to use latex gloves to hold frogs. As it turns out, latex gloves have chemicals much more harmful than things you normally find on hands (there was a recent peer-reviewed journal paper published on the toxicity of latex and nitrile gloves to amphibians).