I've heard that they could pose a potential threat due to their sap. That said, I've used them for years and haven't seen any ill effects. They are widely used and I consider them to be a good versatile option as a basking/hide combo. If you notice one leaking sap (which I haven't seen before) you could rinse it off and bake it in the oven on low (250 or so ) for an hour and really dry it out which should take care of the problem. I really wouldn't worry about it though.