The frogs were produced out of the waters, but the lice out of the dust of the earth; for out of any part of the creation God can fetch a scourge wherewith to correct those that rebel against him. This plague was probably sent because it would be peculiarly grievous to the Egyptians, as being a very cleanly people. According to Herodotus, their priests were wont to shave or scrape their whole bodies every third day, lest any lice should breed upon them.
Related Commentaries of Exodus 8:17
Exodus 8:17
17 And they did so; for Aaron stretched out his hand with his rod, and smote the dust of the earth, and it became lice in man, and in beast; all the dust of the land became lice throughout all the land of Egypt.