Bible Dictionary · B
Blains
Occurs only in connection with the sixth plague of Egypt (Ex 9:9, Ex 9:10). In Deut 28:27, Deut 28:35, it is called “the botch of Egypt.” It seems to have been the fearful disease of black leprosy, a kind of elephantiasis, producing burning ulcers.
From Easton’s Bible Dictionary (1897), by Matthew George Easton.