Evidence that the dust of Goshen turned to Lice

Even though the Bnai Yisrael were not subject to any of the plagues, there is evidence that during the plague of lice, even the dust in Goshen was affected. Rabbi Sorotzkin in Oznayim LaTorah explains this in Vaeirah 8:13 based on Bereishis Rabbah, chapter 96. Yaakov Avinu asked that he not be buried in Egypt and insisted on being taken to Mearas Hamachpeilah to be buried with the other Patriarchs and with the Matriarchs. One of the reasons given is that the dust of Egypt was going to become infested with lice during the coming plague. It appears from the way it is presented, that the dust was infested by the lice so that the Egyptians could not run to Goshen for safety.

Mishnas Rabbi Eliezer (chapter 9) states that as a result of this plague, the Bnai Yisrael no longer had to make bricks, because there was no longer any clean earth to use as the raw material. Had the lice been kept out of Goshen, Pharoah would have just moved the brick making factories there.

Another reason is that Pharoah was able to use this as an excuse to refuse to believe that the Bnai Yisrael were not affected by the plague. He was able to insist that since the lice appeared in the area, everyone living there must have been affected.

Another point about this plague is that the Priests and Nobility were phobic about lice. They were the first group to shave on a regular basis. The priests, for example, shaved off all of their body hair. When the plague occurred, they paniced immediately.

Vaeirah - The original "Green Line"

Rabbi Sorotzkin in Oznayim Latorah (Insights in the Torah) Va'eirah (7:27) explains

27: But if you refuse to send [them] out, I will strike your entire border with frogs.

 The frogs established the borders of Egypt.and did not go one step over the border into a neigboring country (Shmos Rabbah chapter 10). This implies that in areas where there was a border dispute, the frogs actually established what the border should be. This forced the Egyptians to admit where they were wrong and forced them to withdraw from areas that they claimed improperly.

Rabbi Sorotzkin points out that the fact that the hagaddah shows each plague as consisting of four (or five) individual components actually explains why this is not stated in the first palgue (blood). The water turned to blood as it entered the boundary of Egypt, but was restricted to the Nile River. Thus, the rest of the borders were not delineated by that plague. The frogs were thus the first plague to show the borders of Egypt.