Do I need to neutralize after using a reductive discharge such as Thiox?
No. You must neutralize after using chlorine (hypochlorite) bleach, but not after using reductive discharges such as Thiox, Formosul, or Rit Color Remover. You need only wash reductive discharge chemicals out with water. Any residual bisulfite or thiosulfate will react with the oxygen in the air and be safely destroyed.