Prostaglandins are one of the important inflammatory mediators that cause pain. The increase of prostaglandins will also aggravate the pain causing effect of inflammatory mediators such as bradykinin. The inhibition of prostaglandins by Bute ointment will also play an analgesic role (the increase of prostaglandins will make pain sensors more sensitive). Histamine is the most important inflammatory mediators of pruritus. Prostaglandins can reduce the threshold of pruritus induced by histamine. Bute ointment can inhibit the increase of prostaglandins and play an anti pruritus role.