When I enter or leave the nether, while the world is loading and I can't do anything mobs can attack me. I don't have any special packs or skins. I lowered all the graphic settings as much as I could. It does take awhile to load, so I could go in with full health and by time it's loaded and I can move I could be half health. Also I dint make the portal, I found a busted one and just replaced the missing blocks.