As the ashes (= God’s wrath) fell “on the earth” (= land, that is, humanity's home), “harmful and painful sores” broke out on the people living there. Though Exodus 9:8–12 provides a parallel, the two events cannot be equated. Aside from this passage (also Revelation 16:11), the term translated as “sores” appears in the New Testament only in Luke 16:21. In the Greek translation of the Old Testament the term is used to describe the skin condition of leprosy (Leviticus 13:18), Job’s skin (Revelation 2:7), and the boil that afflicted Hezekiah (2 Kings 20:7). It is also the term used to describe the ailments that follow hardening in sin (Deuteronomy 28:27, Deuteronomy 28:35). Of importance, though, is not determining exactly what medical ailment is meant; instead, the accent needs to lie on the adjectives used here: “harmful and painful.”
2 So the first angel went and poured out his bowl on the earth, and harmful and painful sores came upon the people who bore the mark of the beast and worshiped its image.