Heat causes inflammation.
I could swear after I hurt a disc in my back that when I take hot baths it makes the pain worse. I saw the physical proof today. I had hurt my hand two weeks ago. The swelling has gone down almost all of the way. Well today I took a really hot bath and right when I got done my pinkie got all swollen and started hurting again. I could actually see the difference. My back is getting a lot better so I am not having pain in my back from the hot bath. I will ice both just to be on the safe side.