applied externally , it is emollient , relaxing , and discutient , and greatly promotes suppuration : if long kept upon the skin , it takes off hair , and always occasions an itching ; sometimes it exulcerates it , and raises little blisters , if applied to a tender part : sometimes , on external application , it allays pain , and even occasions sleep : but it must by no means be applied to the head , especially to the sutures of the skull ; for it has been known to have the most terrible effects in this application , and even bring death itself .