J-Kat's Ciderm Shampoo is a "two part" shampoo and requires mixing before use.  When Part A and B are MIXED, the chlorine dioxide mixture will be effective for 3 weeks.  Mixture after that is still good as a luxurious shampoo.  UNMIXED Ciderm Parts A and B will last for 2 years and more if kept cold.  Mix as you need it or use within 3 weeks.