Question: what is the difference between nioxin 1 2 3 4?
Answer: What is the difference between the Nioxin 1 and Nioxin 2 and 3? Nioxin 1 is for uncolor treated thin hair to add volume. Nioxin 2 is uncolor treated hair that is thinning helps to stop hair from falling out. 3 and 4 are the same as 1 and 2 but for color treated hair.