The moves came before the second game of their series against the Houston Astros on Wednesday.
Lewis strained muscles in his right side during spring training and went on the disabled list. He started a rehab assignment on April 14. The Reds signed him to a one-year deal in January, hoping he could play left field and bat leadoff occasionally.
Hermida was called up on April 18 and started three games. He went 2 for 18 with one homer.