osteoarthritis
"When I lay in bed with osteoarthritis pain and nerve pain...this tends to give a warming sensation to a bit burning which takes my mind off the nerve pain and after a bit (and with my pain meds) I can fall asleep.  If you like hot showers in the morning it may warm up a bit while in the hot shower.  I wont live without it.  I only use it at bed time and when the pain is to great to fall asleep."